u/Ultrafastegorik

i have been playing the flute for 10 years now, and have decided to start learning bass back in february.
i can play stuff like some tool, hysteria, and some other kind of intermediate stuff, but whenever i try to improvise on the spot or improvise to a song, its really hard for me to do so, i am good at improvisation on the flute, yet i barely can come up with a bassline for any song.
but i understand that its not immediate, and it takes some time, so my questions are:
what should i learn to improve?
and i have also noticed that specifically on bass, for some reason when i try to record it, i play a tiny bit before the metronome, not the tempo, because if i move it forward my recordings fit, but specifically the metronome, how can i prevent that?

thanks :)