I'm watching some random videos involving smd boards.
What is the cream that is used at 2:18?
Doesn't he need to add some soldering after removing the damaged component?
I've seen that he uses hot air. Which temperature should be ok?
The 'cream' is thick flux. Probably Amtech 559 which is excellent stuff.
The problem with really small SMD stuff is that unless you are 20 years old with the eyesight to match, you will certainly need a stereo microscope to be able to see what you're doing. Once you have such a microscope, you can solder many components by hand with a soldering iron, but for removing multi-pin devices, you're still going to need hot air.
There's normally enough solder left on the pads to not need any more adding. However, if the board is using lead free solder, I'd clean the pads afterwards and use leaded solder to complete the repair as it's so much easier to work with and requires lower temperatures.
As to specific temperature settings, you won't generally find hard and fast numbers. This is due to several reasons: a cheap hot air station isn't going to be hugely accurate and also, it's not applying heat at a fixed point like a soldering iron and the actual heat achieved is going to be dependent on not only the heat setting, but the size of the nozzle and the distance from the circuit board. The type of solder (leaded or non-leaded) is important as well. Leaded solder melts at around 183°C while lead free solder melts at around 50°C more. So the best approach is to learn which temperature your particular hot air station and technique requires by experimentation.