I hate thermodynamics and electricity along with everything related to these things. Mechanics is easier but gets complicated after a while and optics is at the same level of difficulty but in optics you face more limits. I really don't understand nothing from Lorentz law,Coulomb's law,electromagnetic force,coils,capacitors and etc. I want to know if it's possible to enjoy engineering if you cheat by using sheet formulas and memorize formulas without understanding them. Can you? How hard can it be to become an engineer?
1. Civil engineers can maybe get by without a full understanding of thermodynamics, physics, and electricity, but only in certain jobs. Many civil jobs require an ability to design simple control electronics (such as water treatment systems, anything with pumps, etc.). If you want to be a mechanical engineer you will need to understand thermo and most of physics. Understanding Einstein's theory of relativity or quantum physics is not necessary.
2. You might be able to finish an engineering degree by using so-called "cheat sheets" to get through parts of physics, chemistry, etc. Will you enjoy it? I doubt it - this would imply that you would be lost in those classes, and that's not fun. But like I said, there are some engineering jobs you can get where you never really need to know those things, ever again. But to clarify, you should never "cheat" - part of being an engineer is being ethical. It's okay to struggle, it's okay to use formula sheets (if they say it's okay).
3. How hard can it be to become an engineer? I guess that is very dependent on you. The coursework can be very hard for some people. Some people simply don't make it. At my school, the wash-out rate for engineering was maybe 75%. You need to evaluate what you really want to do with your life. Maybe there is another way to get into the job you are imagining. If you really, really want to be an engineer, that's a good start. Attitude is everything - a sincere desire to become an engineer, combined with a strong work ethic might be enough to get you through. Learning some of this stuff is hard! I think most people require multiple attempts. You have to make sure your expectations include spending hours, every night, working and re-working problems, and then self-checking your answers to see if you are correct, and repeating until you understand it. So in other words, "hard".