It is important to establish a written lease agreement when you rent an apartment / room and to be as detailed as possible. There are several points that should be included in a lease agreement. There should be information about the parties, that is, the tenant and the landlord, the rent, the rental period, the right to use other spaces if possible(such as attic storage, etc.) and other details such as furniture and garbage collection.
Contract templates are available at Hyresgästföreningens website
You can also buy contract templates in a well-stocked bookstore.