Calculator Challenge - HTML, CSS and JS

I had a big difficulty on establishing a functional and 'simple' logic flow, had to rewrite it a few times to see where I was going. Basically I had to eliminate all the wrong ways of doing it to find the right way, lol! But, after leaving the code away a little bit, my mind gave me a flow that I should try. It had so many bugs tbh, but every bug I found was adjusted. If you find another one, please tell me! I will be so thankful!

Great challenge tho, it took me out of the box, for sure. Thanks!