The macbook pro stuck on the white start up screen

Hello.

I was upgrading the macbook pro mid 2012 few days ago to the HighSierra. Firstly it was okay but the start up took more time than before.

I bought this macbook pro last year. But I still found the data saved (with the previous owner user) in my macbook. Yesterday I deleted some of his data because it took a lot of memory since I think that he won't look for his data to me.

After deleting, I shut down the macbook. Everything is okay. When I turn on the macbook, it stuck on the white start up screen. It takes more time than before and nothing happened after that. I already reinstall the osX but it's still same. Nothing changes. Stuck on the white start up screen.

Could you please help me?

Thanks