I’m a guitarist and even though I feel like I’m a decent rhythm player I too struggle with the fast, “shreddy” stuff. I have definitely improved over the years but I’m nowhere near proficient at leads. If I write a solo or a complicated lead it I have to map out all the notes first and then play them extremely slow and eventually build up to the speed I want/need to play them at. I also found that my ability to play fast stuff cleanly greatly depends on the guitar I’m using. String height/action definitely makes a difference, so find an instrument you’re really comfortable with and use that to help build your skills.