Somehow I think you can improve by yourself but if you don't even have the basics right, this improvement is going to take a very long time. One way around the problem is to take cheap group lessons with a good tennis coach. I grew up in Singapore too and when I was about 14 took group (of 4 people) lessons from a tennis coach for 12 lessons (1.5 hrs weekly). He split the 12 lessons into 4 sets of (3 forehand/3 backhand/3 serve/2 volleys/2 game play). It was a good introduction as he worked through the grips and the proper arm mechanics of each swing. He broke down the footwork involved and the timing of the entire motion. And when you're actually deploying the swing motion, he can at least observe over time and comment on what you're doing wrong. Most of the time, beginners have problems with 2 things: footwork (getting yourself positioned right to take the ball) and swing (mechanics of the swing ). You need a trained observer to help you work through these things. Once you have the basics, you can do the rest yourself and from alot of playing.
After that, you should go off and practice yourself for the rest of the year with friends or a ball machine. In that time also, watch alot of tennis and you'll at least understand what the players are trying to do and observe their mechanics.
I hate to say it but you can't self-learn and self-actualize. If your friend is better than you, in turn, he's teaching you how to play and no matter how unprofessional it is, you are getting trained by him. 2 people who can't play cannot stroke together and learn together. One of them must have at least had some formal coaching.
