In short
It really depends on the audience, so think about their needs, verify them and adapt your structure based on what you've learned before even starting the project.
The different levels of depth
Depending on the audience, your report will have less or more details.
Teachers and colleagues: Give many details as they want to either benefit, or verify each step of your thinking.
Your boss: Doesn't need to know everything, but still might want to have the possibility to get access to the methodology.
Executive level: Stay short. Be focused on the impact of the work (that it had or will have) and the optics (how did people react to it, or have reacted to it). And use the language of key numbers to prove your work.
How to learn what a particular audience wants
Good ways to learn what people need or expect are to:
Ask them what they expect to see
Ask them to share previous presentations they found especially good
Show them a prototype of the presentation (structure with filler words) and ask them what to remove or add at the start of the project
Elements you could put in a report
Here a few elements that you could put in a report. Think about these elements not as elements you have to put in your report but rather as possible Lego blocks that you can select if they make sense both for your project and your audience.
What it means
Summary
Recommendations
Solutions / Answers / Results
etc.
How we worked
Methodology
Validity
Research question
Limitations
Biases
etc.
How can we go further
Future research questions
Interesting learnings out of the scope of this project
Appendix
etc.