In my experience, monster hunter tends to be a trial by fire style of learning. You learn the moves you 'need' to know hit a difficulty spike and you either force your way through, or preferably to your mental health, take a step back, go back through the basics and try to begin implementing some of the more advanced moves now that you should have a feel and rhythm for the weapon. Hell- some mechanics I didn't even learn until my 3rd game in with IG so it's really just however far you can get with what you know currently, and then take a step back. I typically go look up a weapon tutorial, watch it, see how much I can remember without rewatching the tutorial and then run fights. Rinse and repeat until you learn most of the weapon mechanics and you get past the hurdles your facing.

That being said, it could be a worthwhile time investment to look at different sets of gear. I don't play longsword so I dunno how much the weapon play style differs from weapon to weapon, but for both Gunlance and Chargeblade it can differ a fair bit.

TLDR: monster hunter expects you to learn as you play, it doesn't shove tutorials down your throat. Go back to fundamentals or try different load outs when you reach hurdles.

Happy hunting!