Recently I have seen over 4000, 404 pages in my webmaster. My site is https://kindergoed.com/ can anyone help me to solve this issue ?
You can use below settings from admin panel:
Admin -> System -> Configuration -> Web -> Default Pages -> CMS No Route Page and select Home page from drop-down.
You must also use rewrite rule in .htaccess so your 404 page can always redirect you on home page. Kindly check and let me know if this solves your issue exactly.