Professionalization of a website made as a hobby by me (I have no studies or experience, I did it using tutorials so it will be easy for experts).
Basically what it does is store, update and display data and images from the database.
I would guide all the data to send or receive in each activity.
The work would consist of replicating it from the beginning using the most current practices and techniques and in a safe and professional way.
Current, modern and responsive design.
Image optimization to save space and fast loading.
Multilanguage (I would deliver the strings).
Of course, it must be compatible with all browsers and not give security flaws or of any kind.