Mit einem enfachen Komma kannst du das Problem lösen.

Telecommunications, engines and pumps, and thermal processes and apparatus.

Bei längeren Einheiten kannst du zu semicolons greifen:

Telecommunications, cell phones, and other devices; engines and pumps, hydraulics; and thermal processes and apparatus.

Mit as well as kann man sehr leicht fehl gehen wenn man sich nicht auskennt.

Good suggestions, Bob C. -- and I very much agree with your comment on "as well as." It's horribly used in translations, simply because the German uses "sowie" or similar. Is it possible that English has less of a problem with the repeated use of "and" than German does with "und"? So often "and" works perfectly for places where the German text finds it necessary to use "sowie" or (my all-time favorite) "bzw."

Thats why I am asking ;)

An example how I usually use "as well as":
"What makes the BLABLA an interesting example is the investor’s involvement as well as the contracting and governance structure."
or
"What makes the BLABLA an interesting example is the investor’s involvement and the contracting and governance structure."

Can I use "as well as" there?

You can, but and is better.

There are very few times when as well as is better than and. Very few.

By the way, the verb should be plural:

What makes the BLABLA an interesting example are the investor’s involvement and the contracting and governance structure.

I tend to use "as well" only in instances when I have a sentence with a number of "ands" connecting two or more nouns (e.g.), followed by (the need for) another conjunction for a second verb.

For me, as well can sound like the introduction to items of secondary importance. Sort of an afterthought.

Possibly used much more in BE than AE.