Why is my transmission shifting hard while driving from first to second gear?

Hello,

Transmission can shift hard for a number of reasons. Could be for having low fluid level or having dirty/contaminated fluid. Also, can be due to a bad shift solenoid or other internal transmission issues.

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

A good first step would be to check the fluid level and condition. If low top it off to the correct level.

https://www.2carpros.com/articles/how-to-check-and-add-transmission-fluid

I have attached the procedure below for your reference.

Let me know of any questions.
Thank you