To beat marth you must not fight him on his trums try to make marth fight in such a way that he not that good. He is going to win air fight all the time and close up. So you must take advages that he lack rng attk and a some what vertical recovly.
Also do relize i fall pray to the lag with online play i get a lot of input lag vs you azula. Offline zss who i love to play is soo much easer samus even because with out such imput lag a samus can rng attk jump spam like it was nothing.