May I move to a different apartment, which is bigger and prettier, during the nine days? There is a signed contract, the reason is an expected expansion of the family. May we paint the old apartment (it’s in the contract, paint it before returning to previous owner) during the nine days?

One should not move to a new loction from the beginning of Av. If the painting can't be done before Rosh Chodesh, or after Tisha Beav, painting is permitted since the intention is not for happiness, only commiting an obligation from the contract. Rabbi Yaakov Ariel