My site http://bepducnhapkhau.vn/ has many 404 errors. I know it through webmaster- aps by Google. Sometime when i try to redirect it, it seems has no useful. It's just one of my problems because there are still many different mistakes. The design of that web was made by a design web agency and i suppose they bought a theme in Wordpress Theme Library and confix somthings. So, the problem is there are many erros in our website from heading structure, analytics data....to the way its perfomed on mobile. I wonder if i should tell them to find these mistake and correct them or order them to built a new one, and if i can find out the cause and fix it by myself?