6.5 hours transit in dubai, worthwhile to go outside ?

Hi ,

I am arriving Tuesday 6am in terminal 3 and leaving 12:30pm from terminal 2, so have around 6.5 hrs transit time.

Is it worthwhile to go outside airport and is it possible/manageable to see something in this time frame ? If yes, what could you recommend ? Also any other tips ideas are very welcome. Also how long it takes to go through immigration/security both going out and coming in ?

I can get visa on arrival. I am from Germany so I have to check if I can already apply visa online ?

Thanks a lot.