Charging

I’ve read about how I should maintain a battery percent of 40-80 to prolong battery capacity and stuff. This made me so conscious about my battery percent and I use my phone almost every hour of the day. I plan on charging my phone when it reaches 30-40% and unplug it when it reaches 70-80%. Question 1, is that okay? Second, will constant plug and unplugging damage my battery? And is overnight charging really safe?

Also I may need battery capacity saving tips :( Thank you!