Can't get Postgresql to run properly on Big Sur

There is something very strange about running Postgresql on my iMac with Big Sur.

One of the things I did was to install something called DBngin, which allows me to start and stop postgres processes. I don't know if DBngin installed postgres or if Postgres comes with Big Sur by default, but when I start postgres with DBngin, a whole bunch of postgres processes are created.

Somehow I also have a psql client on my system which, on each invocation, starts and attaches to a postgres sever. So far so good, in that psql behaves exactly as expected. I can use it to create databases and issue SQL statements.

One thing I need which is not on my system is pg_restore. So I went to https://postgresapp.com/ and installed postgres from there. What I got was PgAdmin 4, which also worked, but did not attach to, nor create, a postgres server. As a matter of fact I could kill all of the running postgres servers and still have a working PgAdmin. Moreover, the databases I created with PgAdmin worked as expected but were entirely distinct from the database I created with psql, even if they had the same names.

So I have 3 questions:

1) how to I get psql and PgAdmin to work on the same databases?

2) how do I get all the other binaries that come with postgres?

3) why doesn't PgAdmin connect to a postgres process?