If I don't understand physics, can I become a good engineer?

Hi Kuong. The short answer is: yes, you can still be a good engineer even if you don't "understand physics". The degree to which an engineer uses physics varies depending upon the type of engineering and career. For example, if you are a civil engineer and design bridges, then you will need to understand stresses and forces. If you are a computer scientist and write Java programs, you will probably not actively use physics during your daily work.  

However, I am sure that you understand physics at some level even if you do not realize it. Do you know why things fall (gravity)? Do you know how we get electricity (electrons)? Do you know why moving objects stop (friction)? Understanding how the world around you works is part of the excitement of being an engineer; we are often asked to take a theoretical model and make it work in reality. If you end up in a research position, you will have to be able to work in the physical world and that means physics. Oftentimes, teams will be established with complimentary skill sets so that if you are not a physics guru, you can turn to someone who is. 

I would strongly encourage you to keep working to increase your knowledge about physics. For example, read blogs, watch youTube videos, and read books such as "physics for dummies" or "There are no Electrons: Electronics for Earthlings" by Kenn Amdhal. These are fun reads to help increase your high-level understanding of physics concepts.