I'm not really a beginner but I do need help so I'd like to get tips on what I should do because when I watch these replays my opponent looks excellent and I just seem bad.
I need some advice :c

I think because you don't have balance, and your opponents have good balance, also sparring helps a bit getting good balance in rpl making or just play some mods like those, also when you do some move don't just extend joint, you can just like one frame to extend and then relax or hold, relaxing and holding are good ways to get good balance.

hope that helped

Aaaand also you can extend and hold your neck to get it : )

Does he look like he has no balance
I don't have the mod for the last one so I'll just stick to the first two.
You are indeed not bad but to me it looks like you know exactly how to move your Tori but have rather no plan what you want to do next. To look rad you have to land in a way which already sets up your next move, not land and see where you can go from there.
I agree on the extend part though, your knee could use some less extended state.

i actually call "balance" to some good position(also i don't know does anyone else call it like that but i call), where you can make next cool stylish move
with a bit realistic and cooler style

good position isn't balance
balance is when you only fall on purpose lol(keep in mind im assuming your talking about sparring) I feel as though you should try
moving more joints at one time, most people tend to keep there joints in a position for more time then needed and it takes away realism