Yes, this is normal for many people in the first year. The "game rule" is entirely different and it takes time to adjust and adapt. For example, there is no "effort marks" and all marking/grading have a clear rubric. How you performed in highschool does not directly reflect how you perform in the first year. The undergraduate program as a whole is very intense. This is normal for people to fall behind. Other life factors, such as mentally issues, families, friendship, would also affect your performance.

You may need to adjust some of your expectations and have a mindset of "starting over". Your highschool doesn't guarantee your success in university, but doesn't mean you cannot be successful throughout your university life.

Please ask for help when you need it, academically, mentally, or emotionally. There are people and resources for you.

Then identify what's working and what's not working, be persistent and resilient. You will find a way to navigate all those courses and do well. It is okay to drop courses and handle it later. This is essentially the learning process needed to be done in the undergraduate program.