What is the ruling on smoking shisha and its effect on fertility, and what is the solution to the problem of infertility for my sister who has been smoking shisha for 8 years?

Smoking shisha is forbidden. The sister's problem can be solved by fearing Allah, obeying His commands, repenting, and frequently seeking forgiveness, for this is a cause of sustenance and children, as Allah the Almighty says: (And I said, 'Seek forgiveness of your Lord; indeed, He is ever Forgiving. He will send [rain from] the sky upon you in [copious] showers and will reinforce you with wealth and sons and will make for you gardens and make for you rivers.') And as the Prophet, peace and blessings be upon him, said: "Indeed, a man may be deprived of sustenance because of a sin he commits." So, the sister should fear Allah and frequently seek forgiveness and give charity.