I have searched for my question on google but i didn't found an answer, i have a deals website (e-commerce) but actually it's not working, it's only online. I'm expecting to remove the content of the website and use its domain for another website e-commerce but with different niche, with new content. It's a good idea? this will not reflect SEO for the new website?
If the site you will be putting on there is something similar, where the backlink environment will be beneficial and also fits to the new website, I don't see a problem. Otherwise, as you mentioned with a different niche, it might be not as good of an idea. In this case it might be best if you maybe look for an aged domain to buy that already has a link environment that fits to your new niche & website.
The main issue that you will encounter is that existing backlinks can become non-revelant which in time can become detrimental to your rankings.
Nowadays it is better to seek out a old domain that has on-topic links or one that has few links to none.
Relevancy is everything! in this day and age .