6: Black's situation on the right side is called the "orthodox fuseki". The sequence that follows should be fine for white, but you might have fun browsing through the other possible responses here

14: Remember the scene in the Matrix where the weaselly guy says, "After a while, you don't even see the numbers anymore. Now I just see blonde, redhead, blonde..."? The go board is like that. I don't want you to see black stones and white stones anymore... I want you to see weak groups and strong groups. Two stones separated by a two-space jump, deep in hostile territory, with no room for an extension on either side: this is the stereotype of a weak group. And you never, ever touch weak stones, as I'm sure you know, because in contact fights, both sides get stronger very quickly. (Trying to keep him from extending down the side is good, of course! But you need to fence him in from a distance. I would probably play C5, but C4 might be better.)

16: D6 is a big move for B now, and the corner is still vulnerable to invasion. wasn't necessarily a mistake, but it's certainly inconsistent with

22: You should recognize that this move creates a type of double wing formation (so-called because the 4-4 stone has two extensions, normally at a slight diagonal, which looks like a bird in flight). If, after W has put together a double-wing formation, W then blocks off the corner, W gets a huge amount of territory in that quadrant. On the other hand, if B invades the corner instead, W's wall will often be too close to one of the wings. For this reason, B often invades under W's double-wing formation as soon as possible. So when you're playing the second wing, you need to ask yourself (a) which way you're going to block when B invades, and (b) whether the wall you get from the invasion is going to be helpful or not. (In this case, the wall doesn't look too great.)

32: I'm sure you've read out the variations by now to see that this was a mistake. The whole sequence through 48 is pretty bad for you, although having made the initial mistake, I think it's forced.

52: The knight's move towards the center is an attacking move: normally, it aims to cut off a weak group from its escape route to the center, but it can be cut easily. Now, look at this board. Which of these groups are strong and which are weak? Should R12 be attacking R18 (which, besides the corner, can capture Q18 whenever it chooses)? Probably not. -------- I think O15 is a good shared vital point for building influence, and P12 is a good point for strengthening R12, but this move is lukewarm and inefficient.

60&62: Awkwardly, these moves leave cutting points at both P12 and P14. It's ominous. I would have hung back a little.

66: This move strikes me as wrong. I think you're ahead. You're in a comfortable position, and you want to firm up the boundaries of your own territory above while at the same time laying the groundwork to reduce B's potential in the lower-center to nothing. By making a weak group that will have to writhe and wriggle it's way out of B's sphere of influence, you're begging him to get strong, drive a spike into your territory, and then start activating aji.

84: I think this is overplay. Think of 82 as a forcing move. You want to stay light for now, be willing to sacrifice stones. The key thing is to break out into the center with K7 or L8. Later you can try to pick up more points in this area.

86: Inconsistent. If you were going to play , why not marry it and play S8? Remember, weak, invading groups need to stay light. Randomly connecting worthless stones to your group only reduces your flexibility, even if it's sente.

90: I like Q7 better. R9 comes under attack, but in exchange you get an attack on N8.

94-97: This sequence strikes me as aji keshi: you don't have any particular use for these stones you have here, so you might as well save the potential for later. (B then proceeds to squander his own options with 99 first: He should play one or two more moves before deciding which way to atari.)

108: The health of L8 is your #1 strategic priority right now. This move doesn't help with that at all. What does it help with - what was your goal here? (Neither does 110, or 112. All of these moves make the black group hunting L8 extremely thick.)

114: Aji keshi. You can always play this later, but later the black stone at P7 may be obnoxious.

116-120: What you're trying to do is understandable, but two things. First, you're playing way too close to black's thickness. You need to jump back when you're trying to seal off territory like this. (Like with nets - as B approaches the new perimeter, you can seal it off.) Second, your weak group still looks dead to me, and I think you should concentrate on saving it first.

128: This is probably better than N13, but you should understand that not playing N13 is very inconsistent. Was your goal just to make a big lump of stones for B to capture?

Next you capture some of B's stones and the middle game ends, so I'll conclude my comments.

Summative comments: Play more slowly. You played the whole game in 10 minutes, a blistering 4s per move. With your added time per move, you can (i) read out sequences, (ii) think about which groups are strong and which groups are weak, (iii) try to think about your priorities and how best to achieve them, and (iv) try to decide whether you're ahead (and able to play solidly) or behind (and need to take risks).

Completely wrong. B's C7 group is not weak. It's the opposite: B's 2-space jump is a good shape.
The meaning of is precisely that C7 and C13 are miai to make a 2-space jump to settle.
Nope. First, B's C7 group is not weak (see above). Second, there's almost no "always" and almost no "never" in Go. Almost. Usually. Maybe.
Every situation is different so we must evaluate every situation on its own.
Proverbs are only guidelines; we must learn when to apply them, and when to discard them. This is not easy.
is bad not because of the strength or weakness of B's C7 group. See amnal's note.