How would you defend against these two attacks?

When I reviewed this game I realized I'm making defensive moves based purely on what I see  with no real guiding principles' on what is typically best.  Be interested on peoples thoughts on what they would play as the defensive move in each situation and why.  Comment 13 & 18 in the diagram with my thoughts!

None of your moves were really terrible, but on many of them I was thinking "eh, that doesn't feel right."

Umm, I guess the overall consequence was you became passive. You were happy to sit back and defend even though you had the worse pawn structure and your c1 bishop was inactive. I was looking for chances to develop the bishop or play f3 or c4. Trading your only good minor piece (16.Be2) felt especially incorrect.

I stopped looking after black blundered the knight, but in the position before that happened, for example, your d2 bishop is embarrassing   I mean, it's almost better to just give away a pawn than get stuck with a piece like that.

There are a lot of things I like about the move 20.a4, but first piece activity, pawn moves come later.

As for your specific questions, sure, Nf3, Ne5 and defending mate with the bishop... those were all reasonable. I don't think those moves are the main theme of your inaccuracies / mistakes.

Oh, I didn't notice how long your comment was on move 13.

Yeah, 13.f3 looked attractive to me... but since the engine likes it, it feels pointless to say I liked it.

Umm, I liked it because pawn breaks favor the side with more active pieces. f3 brings 3-4 of your pieces into play on the kingside, meanwhile black only has 1-2... so this pawn break will favor you. Notice on move 18.f3 you only get 1-2 active pieces while black already has 2, so it's not very attractive (and the specific tactics make it even worse than merely unattractive).

As for worrying about weak squares, it helps to do things like pretend your opponent gets 3-4 moves in a row... how many attackers can black add to f2? How many attackers can black add to the h4-e1 diagonal? Or the g file? Questions like that. Because yeah, 13.Kh1 does weaken f2, but you shouldn't care because Black can't gang up on it. Weaknesses aren't just formations you see in books (backward and isolated pawns for example) they have to be those things AND your opponent has to be able to bring pieces against them. If your opponent can't then it's not a real weakness.

Kh1 doesn't look like it weakens the f-pawn, or at least it won't be noticed in the foreseeable future. If the f-pawn ever does come on to fire, you can trade it off and break the center with a move like f3 or f4. Generally; I'd want to stay away from passive defense (such as Bf1), and try to find a more active way of defending which doesn't give my opponent too much tempi. The whole idea of Re1 and Bf1 kills the bishop for a move, which Black can take advantage of immediately with Na5, preventing any c4 pawn pushes, and preparing to anchor the Knight with b6. Admittedly, if your position did not have such a pawn structure weakness such defense would be fine, but because there is, Black can use their extra tempi to improve their position and further weaken yours.

All your moves were quite natural and principled, but, as always, every position is different in its own way  Nothing really significant to improve here.

f5 looks like it weakens the a2-g8 diagonal, although reinforcing the e4 pawn. Perhaps White could undermine this weakness with c4. However, all things considered, moves like f5 are never out of the question.

Thanks for the responses fellas!  Appreciate getting feedback talking about ideas rather than just lines being thrown at me!

They castled on move 8, so my response would be to forget about castling, play pawn -h4 and start launching pawns & pieces down the right hand side of the board...

....which is probably why I've only drawn 12 out of 578 rapid games!

First of all the opening was terrible and that is not how you suppose to react when black plays marshal defense against queens gambit which is an inaccuracy on move 2

Take space in the center and this is a sample line many more lines are possible but the key is to take sapce

Bro r you alright and all okay?? 

4.e4 is the stockfish 14 top suggestion and also the main line 

Don't write anything like a fool without analysing 

And also 4.e4 is the most played move in almost every database

The Bf1 defense is the most robust choice for the long term and you keep the tabletop pawn structure intact so that was a good move.

Kh1 is unnecessary since no checks are incoming plus you want to prepare for getting your king to the center.

As you probably know, you always want to prevent any checks on e3 in such a position, but your structure had already accomplished that.

The 13. f4 suggestion seems counterproductive because black has f5 and now an almost indestructable pawn triad. You always want to keep the opportunity to attack the tip of the pyramid.

So to me, a continuation with f3 makes most sense, working toward e4 with an incoming bishop threat against the queen and rook lifting opportunities to demolish black's kingside.

I think it's best to just check the engine evaluation for the most accurate moves.

I agree with Optimissed. I also liked 13. f4 as my first instinct. If Black takes en passant, possibly recapture with the rook (with thoughts of moving white rook to g3, and then pushing the e pawn to clear the diagonal for White’s dark-square bishop). 

f4 is also attractive to me because it hits the black queen, and I always think it’s more fun to be the aggressor. 

In the position at move 13, Black’s pawn on e4 seems like a huge nuisance. It makes it difficult for White to get any pieces over to the kingside. And the black queen and bishop (and even knight) have all the space in the world to come in as they please. I think that would be enough to convince me to push f4.