temu product brand

The angle of the second hand was slightly off.
The instruction manual says to replace the battery with a new one, but is it a mistake to replace the main unit with a new one? I don't know how to replace the battery when it runs out, so I would like you to tell me.

temu product brand1pc Watch/ 1pc Stylish Trendy Business Men's Canvas Strap Casual Sports Quartz Watch & 3pcs Green Braided Bracelets