Two 8 lb dumbells and a 25 lb dumbell. Since I'm very young, and weak, I can't curl the 25lb one.. (with one hand, but two hands is okay)

1. Any ideas on what type of exercises to get arm strength?

2. Any idea how many repitions and sets to do of each one?

3. How long, (can it be estimated?) will it take before I can curl 25, when I can do about 10 now?

4. I don't really care about any other part of my body right now, just arms.

Any other tips will be appreciated.