Convert Access database to web

I have created and maintained a database in Access for a veterans organization over the last 11 years. As I approach 80 years old, I am concerned about long-term maintenance of this database. Access does not seem to be used much here in New Hampshire. I have been considering conversion to the web, hopefully a format much more maintainable in the long run. The database is quite complex, with 70+ tables, 660 queries, 100 forms and lots of code. I have been playing with various PhP application builders, with limited success. None of them seem the deal with complex master-detail relationships very well.
Anyway, what I am looking for is thoughts on alternatives that I might consider. I need some new ideas, or discussion of possible approaches.
Any contributions would be helpful!
Ron

Maybe some of the following you already know, so apologies in advance.

Basically there's two aspects to it: on the one side, transfer the backend (tables + queries) part and the frontend (forms and reports) part.

The backend part is relatively easy to convert to other database engines the web developers can reach. There's many: MySQL, MariaDB and PostgreSQL are some of them. There may be open table converters which can create the tables and transfer the data to those database engines, if not Navicat can be used for it. Querydefs as defined by Access may be ported as views or stored procedures although that's a little more laborious to perform since the SQL syntax itself varies across the engines.

There's no cheap and easy way to convert the forms to web version, so the PHP or other language devs will have to do that from scratch. The best you can give them is the database schema so they can figure out how to carry the input of the data and apply the proper code.

Thanks for your response. I do have the database backend converted to MySQL: interesting that you group queries in the backend. Perhaps views? I have not yet tried converting queries: I am stuck with my PhP generator creating a form even vaguely like what I want. Steep learning curve, support is terse, and expensive.
However, you seem to support my general approach, and I was really concerned that I was missing some obvious alternative. This is going to be a huge commitment of time for me.
Really appreciate your thoughts.
Ron