advise needed

Oh my goodness. I have to comment here because some of the advice you're getting is a bit sus. Oh sugarcane farms, sugarcane farms. I've been building them for almost a decade. Optimizing them has been taking up room in my brain for such a long time.

First you need to know that sugarcane has 16 growth states. The block doesn't show any texture change but sugarcane will over time receive random ticks and count up in state. Once it has fully grown only then will it create a new sugarcane block above. Crucially once the sugarcane block reaches it's final growth state it doesn't reset. So if you have 1 high sugarcane and you harvest it immediately after it grows 2 high that only requires one random tick. However if you wait to harvest it until it's 3 high that would require 17 random ticks (which will take a LOT longer). This also means if you want to benchmark your farms you should wait until all the bottom sugarcane blocks are fully grown because freshly placed sugarcane will give you a very slow start.

Generally speaking there are two types of sugarcane farms that I see.

First, there are one-piston-per-sugarcane farms. Logically the two ways to optimize these farms are to break the sugarcane asap after it grows and reduce the resource cost. The farm you have right now is ok. You essentially have a clock that pushes the pistons periodically. Testing will tell you if you have the time dialed in, I'd suspect that a faster clock will be more efficient so that would mean moving the observer one block lower or even stripping out the current design for a different style of clock, but you would want to test to see how that turns out. The sugarcane can't grow on the tick where the pistons are extended so eventually that will interfere with the farm but it's not an issue until you have a fast clock going. If you want the farm to harvest immediately when the sugarcane grows, you either need an observer per sugarcane OR you need to use a budded piston setup. The budded piston setup the way I built it in the past would essentially mean that if you have 13 sugarcane you need 14 pistons + some other components like Redstone and 1 observer (IIRC). Sorry I don't have a tutorial, no one makes these farms anymore since they added observers. Don't worry about that because we can do more optimal than the one-piston-per-sugarcane farms using the second type.

Second there are slime-block/honey-block sugarcane farms. These farms push some kind of slime contraption across a field of sugarcane. They are a lot more resource efficient in terms of the redstone because the mechanical part of the farm can harvest a much larger area. Observers have made "sweeper" flying machines really cheap. 2 pistons, 2 observers, and you can build a sweeper made out of slime or honey blocks out to just short of the push limit in both directions. The key efficiency observation with this second type of farm is that sugarcane is cheap so don't worry about how fast you harvest an individual sugarcane, instead figure out how to pack a lot of sugarcane into the farm. For example this design is pretty close to optimal. The main problem with flying machines is that it's possible for flying machines to break on servers. This is a lot less common then it used to be as some bugs have been fixed. I think that this is much less of an issue today than it was in older versions so I think that if you want to optimize all of the best designs are going to involve slime/honey flying machines.

As a third consideration I think that your collection method can be optimized. Increase the random tick speed in your world and you will be able to test and iterate on your design much more quickly. What you will find is that sugarcane when broken likes to pop and glitch all over the place out of the farm. The pistons pushing sideways will from my testing cause more drops to escape than pistons pushing downward. This is another way in which flying machine farms are more efficient because the whole area needs to be covered in a collection system drops can only escape at the edges vs with one-piston-per-sugarcane you can usually only do two rows at a time.

In fact this brings us to the fundamental problem with optimizing sugarcane farms. As a certain point it's just a matter of scaling up whatever design you find interesting at the moment. If I'm going to build a sugarcane farm these days the important thing to me is that the design is not boring. I've build too many sugarcane farms and so it's nice to pick something that's a bit different than what I've tried before. Scaling up will hide a lot of inefficiencies. My advice would be to take your current design even if it's not perfect and figure out how to scale it up. For example instead of one line of sugarcane mirror it so that there's two rows of sugarcane that way sugarcane that might escape will instead just land in the other row.

If this wasn't enough information feel free to reach out and have a good day.

You'll want to put the observers directly on top of the pistons, and instead of having one, have an individual one for each piston (not required, but it would speed it up a lot) Those observers should be facing the sugar cane. Then, place a block on the back side of the observers, and a piece of redstone dust under that block (you can place blocks down so that you have somewhere to put the redstone dust)

In my experience this is the best way to do it. Happy farming!

Best way to improve output is to simply build more layers. Sugarcane can't be force grown so you max out as much as you can on possible tick rate in a chunk.

Replace bamboo with sugarcane. Connect all pistons with redstone. Add observer on top that looks at daylight sensor and connect it with rest of the redstone. That will activate all pistons few times during the day and you don't need observer for every sugarcane. You can add one more observer with daylight sensor set to night mode so farm will activate during the night too. This won't improve the rates (if we don't count replacing bamboo with sugarcane) but it's much cheaper than having 1 observer for each sugarcane like others recommended, especially for bigger farms.

You can improve output by 10% by replacing that one bamboo with sugarcane. Other than that, just tile the design.

Isn't there a way to deploy bonemeal to accelerate growth? Either that or scale it up to the output you need.

Use an observer on a daylight sensor instead of the growing bamboo. It'll trigger a handful of times a day and not wait until the bamboo is tall

Quit the game