Audit of the site on OpenCart and evaluation of error elimination

It is required to conduct an audit of the site on OpenCart 2.3.0.2.3 in terms of programming errors and layout.
The purpose of the audit is to find a specialist who in the future will be able to correct errors and carry out further development of the site on an ongoing basis.
The winner will be the person who gave the most detailed and understandable recommendations for a person who has little understanding of this.
Website: ant-snab.ru