Cheap greenhouse

Hello! I bought a cheap “greenhouse” thing off Amazon for my indoor house plants. I would much rather keep them inside but that isn’t an option as of right now due to space and cats. I’m here asking for suggestions or tips on how to keep my plants safe while they are in there temporarily, until I can actually get them a proper greenhouse. I have a small heater that is keeping it warm on colder nights, but I’m finding it hard to keep heat in when it’s not sunny out. Today was the first time it’s actually rained since I put it up and there is a lot of condensation on the walls, none of my plants are touching the walls but I am worried. Is there anything I can do to help fix the condensation? The sheet on top is to protect the leafs from getting sunburned lol. Thank you for looking and reading, any advice is appreciated.