login page is’t found anymore

After changing the theme of my website to twentyseventeen I can’t login anymore. Both Firefox or Safari can’t find the page which is used to login. I can reach my site with FTP, but I don’t know where to look for.
Is there someone who has the same problem or who can help to solve it?

I don’t know which version of WordPress I’m using, but my site is recently updated automaticaly.
address;www.alicewbakker.nl

thanks, Alice