wohin soll ich meine Heizmatte plazieren?

I’m no professional.. but I’m not sure what you’re talking about exactly. You should have a tent canvas with another bottom part that’s separate that ties to the tent poles that’s like a canvas tray that makes cleaning up easier when needed. Heating pads - you usually want for younger plants to boost temps and what not. If you have a whole tent full of plants and only a small heating pad I’d probably just put it in the middle under everything. If you upload some pics of what you have going on now that’d help