Help

I have an upgraded race clutch so it bites harder; I’m pretty good at driving it I’d say but I always struggle when going from 2nd to 1st. It jerks a ton. Some tell me if I’m taking a turn etc just to stay in 2nd but sometimes I dip below 10mph while in 2nd and I can hear the engine boggling. Some say to not do that so idk what’s right vs wrong. How do I get down to 1st smoothly. Like sometimes I’ll take a turn and I go down to 2nd so im not going too fast and it just gets all jerky and stuff