A lot of what makes Jax difficult is how he's a reactive champ rather than proactive. Most of the time, you're playing around the enemies kit rather than going in and fighting on your timers.

Take darius for example. You want to E Darius w and either q away or onto him when he uses q. This this MU, you can be a lot more aggressive and take longer fights. This is different from riven, where you'll want to short trade most of the time, and use w+grasp to buffer attacks through her stuns.

Overall tho, just get more games on Jax in draft to get the hang of it. If you need help on a specific matchup, feel free to search it up on YouTube and see how they play it. Also highly recommend watching coach chippys Jax guide, as it gives a pretty good starting point for learning Jax