Hello @Mara,
look little about that. A summary I found :
1. Create relevant online consumer protection rules (GDPR)
2. Focus on personal data protection and security
3. Ready to develop a good relation with your customer, reactivity, Chat (why not), good support
4.Develop the reviews are very important
5.Allow the customer to rate your work.
6.Of course, website in SSL
7.Quality Website design