Thanks to you both
As you wanted to see the progress I'll post some new pictures:
On 11/7 I started by putting the tree next to a window and watered it every day. I also trimmed some branches and cut off yellow leaves.
After almost 14 days it started to look better:
Then I bought a bonsai soil mix and changed it. I left it in the old pot because I haven't find anything suitable so far. I also moved it outside and put it on the balcony near the wall. I still water it every day and next week I plan to start use some fertilizers.
I does look more greenish and happy:-) Today it looked like this: