Bachelors thesis on my desired topic already written by previous years students
Unlike dissertations, bachelor’s theses need not be on an original topic or advance the frontiers of knowledge (although those goals are desirable!). A bachelor’s thesis is intended to show that the student is capable of synthesizing information to produce a useful result via research in some form or another.

So unless the school has a requirement that topics cannot be repeated, there is no reason why you shouldn’t be able to produce a work on a similar topic. That said, your work should not be identical to the previous work (which you should cite and discuss in your thesis!)