@lianarules
For Physics Chemistry, You need to work Extremely Hard. For Physics, Try "PHYSICS MATTERS" and For chemistry try "CHEMISTRY MATTERS" in my time, these books provided great informative and fun learning. I Recently saw these books at cousins, and new editions are totally impressive. Take a weekend out and study one of these from start. then immediately pick up past papers and solve some of them.
Now for Addmaths. Man! O level addmaths is exhausting! I worked daily 2 hours self study to improve. What a failure I was in addmaths! but then I took a VERY VERY expansive tutor. at that time, (8000 for only maths & addmaths and 3 days only 1 hour time). He used to hit me with sticks! Addmath was compulsory in my school too. Well, You must must must....
- Have GREAT grades in addmaths and maths.
- have atleast satisfactory grades in chemistry.
- have Good grades in physics.
- have enough credit points (volunteer work etc.)
To have a chance at a good job as mechanical engineer.
I still remember the coffins of little hope I took with me each day, The sacrifice of the Vanity of Human hopes I gave. I gave up on meeting relatives. I gave up on going restaurants. I gave up on meeting with friends. I gave up my social life. Believe me, Life changes after O/A levels. There is an end to suffering. I just used to think of the struggle through which my father was teaching me in such an expansive school and this motivated me. Now we are much more settled Mashallah. I have social life, I have good friends too! Just Keep focused, and you will make through the other side.
You can also opt for automobile engineering if that is your interest. It is increasing in scope and you could do extremely well in that, I sense that it you...