Massive strength gain?

I started doing weights not long ago, and in 3 weeks I could do double the reps and double max weight with bicep curl, so I started to do more than just basic exercises with dumbbells, and have moved on to things like bench press. Again there was the same amount of strength gain in such little time. My muscles heal completely in one night, sometimes two nights, and the next day after doing weights my max bicep curl increases by 0.5kg - 3kg.

Is this massive strength gain normal and most importantly, healthy?