Senior -anything- only ever comes with time. Years and years and years...
I think you would play a lot better if you played slower. Practice nothing but short hop forward airs while moving backwards (use the c-stick to do the forward air and then pull back). Cut down on the counter because the lag will get you punished (it's too much of a crapshoot to use: it if works it only does 6%, if it fails, you get destroyed).
From the edge, learn your options. You can edgehop an attack, ledgedash, do your getup attack, roll, get up (just press forward), jump, or drop down and jump and grab the edge again. You should mix these things up CONSTANTLY and try to use less of the laggier ones (roll, jump, attack).
DI will help you live longer. This is the skill of changing the trajectory of getting knocked back. You can only change the direction, not the power of the move that hit you. The secret is to press and hold up when you are flying in the air. This will convert your horizontal momentum into more vertical momentum, giving you more time to live and also getting you closer to the stage.
Lastly, a grab game is important. Grab someone and throw them and don't attack, just watch what they do. Grab them again and throw them again and just watch them. Memorize the methods in which they recover themselves and look for openings to hit them with a nair/fair/fsmash/ftilt/dtilt or another grab. In fact, never stop looking for openings. Spend more time watching the opponent than yourself.
I only wish I could teach these things better. Keep it up kiddo.
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ill be shore to check in on this thread to help you out if its needed