Firstly who’s the character that you play? Secondly, you need to work out how you’re getting damaged in the first place, bad blocking, bad spacing/zoning(They jump in alot on you and you can’t block it due to a sweep, fireball etc), trying to atttack and getting counterhit, you missing combos?
Now this is a bit hard with the little information you’re given but generally you need a gameplan. You can’t expect to win if your gameplan isn’t solid enough to net you wins else than your opponent playing really bad, basically not making mistakes that give you easy damage, punish, anti-air etc. Some gameplans are knockdown and pressure(This is pretty much rushdown.
Start learning knockdown setups, aka okizeme, what you can do after knockdowns is highly important). Depending on your character it might be good at zoning(Anti-air and fireballs).
Blockstring properly, if you’re getting Reversalled , thrown, or even normal attacked/specialled, make sure you’re chaining and not linking. Linking means any timing mistake you make in your blockstring you’re going to be punished. Also the nature of linking makes it so you can get DPed, make sure you’re chaining and the execution is clean. With blockstrings you can stop it at any point, usually they last 2-4 chain hits, incase they’re trying to reversal you, then start it back up again if they’re not attacking. Learn to counter what they’re doing if they’re stopping your blockstrings in its tracks.
Don’t try anything you’re not capable of, combos will come out in training room, but your reactions timing and focus won’t be the same in the real game, you either need to practice and fail in game until you can do what you do in the training room in-game, or stick to what works and practice “winning” against players than “improving in execution and what not”. Sometimes you can’t anti air effectively if your goal is to win rather than just work on your anti-air, then just block or use an anti-air that’s reliable(eg Ryu’s C.HP is easy to do compared to Shoryuken) and really easy to execute. Sometimes its better to play safe than to go for damage, damage opportunities will always present themself, it’s alright to miss a few compared to getting hit whilst doing so. Again the difference is between improving yourself and playing to win here. It’s good to try and improve your execution but at times it’ll cost you a game or alot of health, work out what your goal is here. With time you’ll improve.
TBH you can probably beat players by just chaining lights attacks if your character has good ones, throwing, and pokes, anti-air and ultra/super setups. Doing combos and what not are going to cost you games until your get them perfected and hit confirmable on reaction. Maybe stick to simple combos until you can truly pull off combos like 90-100% in training room on both sides say 10-however many times in a row.
Just work out what’s costing you the game, and working out how you’re suppose to get more damage is highly important.