reverse the car hard to backup?

Hello,

Let's start with the basic.
Anytime you have issues of the transmission shifting issue, check the fluid.
If the fluid level is low or dirty/contaminated, it could make the transmission have shifting issues.
Make sure it is a the correct level and in clean/good condition.
When you check the fluid level, make sure that the vehicle is level and the engine is at operating temperature.

https://www.2carpros.com/articles/automatic-transmission-problems

This could also be due to the shifter cable not selecting the reverse when you move the shifter lever to the reverse position. This could be due to a stretched cable and just need to be adjusted.

I have attached the fluid check and the shift cable adjustment procedure for your reference.

Please let me know of any questions.
Thank you.