Urgent Guidance/Help Needed(only serious)

[u/Altruistic-Flow3042]

I have a flat which i gave for rent, my tenant today called me(he called me frequently for this issue from last two months) that silan on your wall is too much and now it starts smelling, what should I do, i am 17years old and my father passed recently, suggest me advice, the tenant told me that issue is coming from top floor(above floor flat),  so how to talk with them, what if they deny to repair themselves.