i am always on defense after a serve.
Serving is a neutral shot, the best case scenario is you get a neutral shot back, worse case scenario you have to defend something. It's very rare to win a point straight off the serve so make sure expectations are correct for when you serve. HOWEVER it is so important because it's the only time in the game where you are perfectly balanced, are under no pressure from your opponent and your opponent can only react to the shot.
Doubles: always get smashed.
Without a doubt you are serving too high (on the low serve). If that is not the case and you're shots are tight to net and land on T, then you need variety in your low serve.
This is due to either/all of 1) poor serve technique 2) good return of serve or 3) poor footwork in response to the return. Focusing on 1) - how do I improve the serve? Already watched countless videos.
Your serve is fine at this level it seems. It's a little high but opponents are not rushing to punish it and are waiting for it to come to them. I think #3 is the culprit (lack of experience maybe) but lets focus on #1 here:
Improve the serve (the question) by focusing on tightness to the net (even in singles) and studying about likely returns. Typically serving to the middle like you're doing is what you'll do most of the time as it'll force opponents to use either forehand or backhand.
@Ffly mentions serving to the T which I actually disagree with. It's a better option when you're serving from the left (assuming opponent is right handed) as they'll take it on the forehand likely which limits returns.
If you're serving from the right serving to the middle gives it to their backhand and it's very easy to play any shot from there.
In short:
- Focus on tight serves to the middle, not the T (IMO)
- study likely returns, and be attentive to particular opponent preferred returns.
- practice footwork (fast to rear court, late forehand/backhand, guarding net, etc.)
I know that's a lot to take in so let me know if any need clarification