I included the five sentences I was most unsure of. Thank you for helping me. It's really urgent.
1) I was very proud of myself when I won a (the) regional roller-skating competition in 1998. (when I scored 4 goals one after the other/when I headed the ball in four time during the final football match of the season)
2) I was proud of myself when I got A+ in maths/I passed my driving test/I passed my school leaving exam (?) with top marks, I took my degree with full honors, I got married.
3) I was last ashamed of myself when my teacher caught me cheating/when my mum insulted and beat me in front of my friends.
4) I once blamed my friend for missing the concert (?). She picked me up too late and we were then held up by a traffic jam. We arrived at the concert hall 15 minutes too late.
5)By the time we got there, everyone had already sat down.
I'm still dependent on my parents since I don't earn any money. I'm going to stay with my family until I'm of age. (?)
1. the, not a -- I don't know what "in four time" means, so I'd leave the words in parentheses out.
2. "school leaving exam" -- I'd call it an exit exam.
3. OK
4. OK
5. OK
Nice!