How long does it takes for the 2 front top teeth to come in after losing the baby ones?

Normally. It can take a few months to even a year depending on where they are when the baby ones come out. If they came out too early expect the perm ones to come in quite a while after. If concerned see your dentist.
Couple months. Usually the permanent teeth help push out the baby teeth, but it may take several months of toothless smiles before you see the permanent teeth peek out.