Please give me tips on re trying to breastfeed

When my baby was first born a few months ago I had planned to breastfeed, I tried to get him to latch a lot and 4 nurses tried as well and he put up a fight every time. he had a tongue tie that we fixed 3 days after he was born and it didn’t help. I pumped exclusively the first month but then we started doing half breast milk and half formula because I didn’t have the time to pump every two hours and lost a large supply of breast milk, i was getting like 7 oz out of one breast and about 5 out of the other, I feel so guilty for not trying harder and I would really like to get my supply back up, but from breastfeeding instead of pumping, has anyone started breastfeeding again after 3 months?? can you please give me some tips, not for just re starting but breastfeeding in general?

I feel like breastfeeding was way harder than expected and I didn’t know as much as I should’ve which made me give up easier. I would really love to try again. Also, I know most lactation supplements don’t work but does eating oats/ oat milk help??