Can I use here in this sentence "damit" instead of "weil" ?
You can write this:
Ich bewege mich viel, damit ich gesund bleibe.
Let's compare these sentences:
- Ich bewege mich viel, weil ich gesund bleiben will.
- Ich bewege mich viel, damit ich gesund bleibe.
In a higher level both sentences express the same, but in a very basic meaning they are different:
In 1 you start with a wish (that came into your mind in the past): "I want to stay healthy", and this wish causes you to move a lot. So you move now, to fulfill a wish that was there before you started to move.
In 2 you have a goal for the future: "I want to stay healthy", and you move a lot to reach this future/prospective goal.
My English is not the best, but I think you can translate those sentences this way into english:
- I move a lot because I want to stay healthy.
- I move a lot so I can stay healthy.
I think, you had this in your mind:
- Ich bewege mich viel, damit ich gesund bleiben will.
But this is wrong. When you say this, you in fact say something like this:
- I move a lot so I wish to stay healthy.
Grammatically this sentence would be correct however the sentence would not make sense in most situations.
In both cases (weil and damit) the sub-ordinate sentence describes the reason why something described in the main sentence is done.
However there is the following difference:
Using weil the "activity" in the main sentence is the consequence of the "activity" in the sub-ordinate sentence.
Using damit it is the other way round: The "activity" in the sub-ordinate sentence is the consequence of the "activity" in the main sentence.
Let's look at the following two sentences (which differ only on one word):
Ich fahre langsam, weil das andere Auto mich überholt.
I drive slowly because the other car (already) passes.
Ich fahre langsam, damit das andere Auto mich überholt.
I drive slowly because the other car shall pass.
A combination of "damit" and "wollen" is however possible:
Die Eltern versprechen ihrem Sohn etwas, damit er auf die Reise mitgehen will.
The parents promise something because they want that their son wants to take part in the journey.