Hi there, and welcome!
I echo 100% of Chew's comments; how can I not? His comments helped me go from DDK to SDK

. I'll try to organize my comments around principles. Note that there are always exceptions to principles. A good way to apply them is probably think "Okay, this move is against a principle, so do I have a clear plan for playing here?" If not, then you probably shouldn't play it.
1-5 All good moves, couldn't have played them better myself. Sticking with the 4-4 or 3-4 around your level is probably a good idea, but not that big a deal.
7 - As Chew said, generally you shouldn't touch a weak stone (often, the diagonal is considered "touching" for these purposes). There are definitely exceptions to this, but if a stone is weak (especially a lone stone) think before you attach/touch. Strangely, attacking moves are usually not attachments, but one or more spaces away from the stone being attacked. In large part, this is because attaching to a lone stone will usually just force the stone to become stronger.
Note that 6 and 8 are bad moves for White. Generally, when you play in the middle of two of your opponents corners (like white did here) usually play on the third line so the stones can make a base. When there are additional stones in the area, you have to adjust. You responses to 6 and 8 should be almost anything else other than an attachment. Enclose a corner, for example. Or play a few spaces away on the third line.
21 - Usually, don't play elsewhere ("tenuki") when your stones are vulnerable. The shape of the L17 stones is really bad, which I'm sure you realized when white played L16. Also, your K5 stones is in the wrong place--it would be better to play at K4 or approach at O3, for example. Or you can even do F3. Again, make sure your stones can make a base and they aren't left "floating."
35 - Good idea with this move - don't get closed in.
39 and 41. Early in the game, think for a minute before playing moves on the first or second lines. If you're going to keep going in this corner, you should continue on the third line with 39 (and not go down to the first line with 41). Why? Think about it: white can't really invade underneath your 3rd line stone, and you're obviously making MUCH more territory if you're pushing along the third (or, better, fourth) line. There is a proverb that says the third line is the line of territory, and the second line is the line of defeat (or something like that). Don't take it too seriously, but think before willingly playing along the second line (unless you have to for life).
43 - Nice idea. This Neutralizes white's strength a bit, while not getting too close (or too far from your corner stone).
90ish - You were able to use the stones around K5 kind of, though you were lucky white didnt handle the situation correctly. You should still get the idea that stones that high don't have a base, and can become in danger very quickly.
153 - Just because you CAN atari and capture, doesn't mean that you should. Here, there is no reason to play to capture the white stones after you've already sealed them off. But if you can't read it out, and you think you're in danger it is okay at your level to play it safe and capture.