Mistakes on the site

Who tried to make their own sites? Need some advice. Initially, everything was working fine. Now all the time there are different errors. I can not understand the reason why.

It is also difficult for me to say a definite reason, because I do not have access to your site. But I can give you the address of this service https://pr-cy.io/ The site has an opportunity to learn about website error checker. I am also engaged in the creation of sites and this service often helps me. So be sure to try it.