Is one who renovates and decorates shops where sins are prevalent, such as barbershops and movie theaters, considered sinful? And is this considered aiding in sin? Is it permissible to give money to someone who will squander it on smoking? And is it obligatory to inquire about how a needy person will spend the money?

It is not permissible to renovate or repair places that are predominantly used for disobeying Allah, because that constitutes aiding in what is forbidden. Similarly, it is not permissible to give money to someone whom one knows will use it for unlawful purposes, because that constitutes aiding in sin. You are not required to ask someone who requests money what they will spend it on; rather, it is sufficient that you do not know they will spend it on unlawful things.