I'm out in my little house in Spain at the moment. It gets really bloody hot out here (tip to self: if the Spanish call something The Warm Coast, believe them next time). Here are some ideas I use in case they help.
Firstly, if you can, cook outside, to avoid putting heat in the house. The slow cooker, the halogen oven and the air fryer are all ideal for this, if you have a terrace or a balcony or something. If you have to cook inside, put the extractor fan on max to try and send the hot air and any steam straight outside. Barbecues are an alternative option of course if you can do them anywhere nearby.
Using the microwave tends to contain heat and steam. Batch cooking, defrosting and just reheating is a good way to cut down on cooking (and if you defrost a portion in the fridge overnight, as an added bonus it will help keep your fridge cool and save on electricity).
Try to minimise the amount of time you cook things for - baked potatoes require a long cooking time, so best done outside if possible, whereas scrambled eggs or an omelette are very quick. Have a go to list of things you do when it's hot - eg roast chicken, tortilla or a quiche from the supermarket, a big box of salad and a tub of potato salad or a few microwave chips will feed you all without heating up the apartment. Have the odd takeaway too if that's an option. Frozen rice or the microwavable sachets can quickly be microwaved, and are much better than all the steam and heat from boiling rice or pasta. Humidity is to be avoided. You can get those sachets of prepared vegetables, stab them a few times and cook them in the microwave too.
As you realise, anything you can do to not create heat in the first place, or let it in, is better than having to try and cool the place down once it gets warm. The coolest time of the day and night is around six in the morning, so throw the windows open then and then close them through all the heat of the day, with curtains and blinds drawn on the sunny side of the building.
Good luck OP. 😊