I would like to add that mal makes things more polite. If you only say "Schau!" , "hör zu" "iss" its more like a commando, but if you add mal to an imperative and say, "schau mal" "hör mal zu" "iss mal" then the sentence is less harsh and much more friendly.

Hi Abdurrahman, like Ramona already explained it's a filler word but I wouldn't say it's stupid. It's more like it takes the formality out of all this. Regards, Marco

In this context it means nothing. :) It's a stupid filler word, a bit like well or just. Well, I think... Just look at that... You might as well say Ich denke... Schauen Sie...