Increasing rounds in DES, increases or decreases the security? I was wondering whether in DES,
if we used more than 16 rounds, the security of the message was increased or actually decreased?
(disregarding the decreased speed of execution / computation.)
Thanks in advance!
Short answer, it increases the security.

The fundamental problem with regular DES is the number of bytes used for the key. It is too low to be considered secure* (with the level of computational power it currently exist, it is feasible to brute force through DES encryption).

Try checking out 3DES article on wikipedia for more info on a better implementation of DES:

https://en.wikipedia.org/wiki/Triple_DES