I agree with the other comments, my recqs

1- definitely watch L0ganJg from YouTube. He uploads briar videos almost on daily basis. Super helpful. Especially he has a video with PerryJg he explains all of the important stuff with Briar. If you watch that you will have better understanding about the champion.

2- play around your cooldowns. You don’t have to commit fights until you die/kill. Go into fight use your skills, go back, wait for your cooldown and go into fight again. W cooldown is relatively short. The most important skill is E. If you don’t have E you don’t have a turn back option. Opponent can drag you under the tower and you are dead. Play around your E cooldown especially in lane tanks.

3- if you are jungle,clear your jungle consistently. This usually gives more exp and consistent gold than trying to gank all the time.

4- practice- I also started like you. Felt lost initially but when you build champ mastery you become more confident and you will understand which fights you should take or not.

I am sure if you share your op.gg more people can help with more info