What makes a good Bachelor's essay? I need some ideas and rules.

For a complete set of rules about your Bachelor's essay, you should consult your school or college. In general, Bachelor's essays are research projects that seniors in college carry out. The essays focus on independent research, and students generally work with a faculty member or professor to craft their research and writing. A good Bachelor's essay examines a new aspect of something you have studied and includes carefully documented independent research. In addition, a good essay makes an argument and defends it using appropriate evidence.
To find the right idea, look at what you have studied. What has sparked your interest? What do you want to know more about? For example, if you have studied history, is there an event, question, person, or recurring theme in history that you want to dig into? If you are interested in military history, you could focus on a particular war, including the reasons that war was fought or first-person accounts of that war. If you studied English or literature in a foreign language, go back and study a book you enjoyed and look for books that are in that same literary movement. You can start by reading literary criticism to try to figure out how the titles are related.
After going back to what you have studied, you will start by crafting a provisional thesis, or main idea, that makes an argument that you can prove. After sharing this idea with your advisor, you will likely go on to do additional research, followed by writing and revising. In all your work, it is important to document and cite your sources carefully to avoid plagiarism and to construct a works cited section. While working, be sure to follow your school's guidelines and deadlines. The link below is to Hamilton College's list of senior thesis topics from 2015.
https://www.hamilton.edu/academics/student-research/2015-senior-thesis-topics