Welcome to the gym and please leave your ego at the door step.

The biggest misconception in weight training is that the heavier the weight you lift, more muscle you will build. This is not entirely true.
The heaviest weight you can lift while maintaining the perfect form, now that will give you the maximum result.

After being absent from gym almost 3 months, my strength dropped, If last time I can bench press 5o-60kg, now I have to reduce it to, 40kg, same goes to my bicep curls and the rest.

It is difficult to start back from scratch, I tried with all my might to lift the same weight like before, and I could life it, but my form sucked! It wasn't symmetrical and I am unable to balanced it.

I have seen many guys in gym struggling with too heavy weights thinking they are doing the right thing and also because they can't let go of their ego while lifting. I am not surprised, I was on of them, most guys think the amount of weight they lift is directly proportional to the size of their dick! Thus we have all this guys working out with heavy weight with terrible forms.

Another mistake I often see is that the tempo is too fast, they will be doing bicep curl up and down so rapidly with no pause at all. This is often done by newbies who think the faster the repetition more macho they are. This is not going to build muscle either, while doing repetition too rapidly, you are just using the momentum of the weight rather than the power of your muscle! The slo-mo works the best! Do it slowly, 10 repetition of 3 sets works fine most of the time, but you can also try other methods such as drop-set, pyramid-set and many more. But always start with the basic.

So my advice to anyone read this, it is not the amount of weight you lift or how rapid is your tempo, it is in the form, tempo and how you contract the muscle while lifting it.

And of course proper nutrition plays a bigger role in building muscle, it is 70% and 30% exercise. More on this later.

Chau.