Évidemment is a very common filler, especially on radio/TV.

We do say "Tu sais/vous savez", sometimes substituted by "Tu vois/vous voyez".

In an informal conversation context and in order to avoid two occurrences of the verb "savoir", I would however translate "I don’t know what to do, you know, I don’t understand what’s happening" by "Je ne sais pas quoi faire, tu vois, je ne comprends pas ce qui se passe".