Asklemmy

If you have space outside, plant native trees/vines/bushes that will help shade the building from the sun if you're getting direct sunlight. You can just do clippings from wild growing plants for free.

timing of the windows opening and closing is key. Also tracking temperature helps, just a crappy thermometer (one indoors and one outside not in sunlight) will let you know when it's time to open or close up.

Concrete/bricks work both ways as a thermal mass, if you can get them cool and covered from the sun it will help cool your area (think of cold concrete floors, I have an inner brick wall that an extension was built out on and it stays coolish). Same with water, most have experienced a cold water pool/pond on a hot day, big blocks of frozen ice can do the trick if you stick to freezing at night.

Free stuff:

• No/less electronics during the day (tvs/chargers/computer), it all adds to the heat
• no cooking during day, cold cuts/food only till night
• Take a nap during the hottest part if possible, or just sleep in daytime and move about at night on off days (something about waking up after a nap makes it seem less overbearing)
• do maintenance on your fans, take them apart and clean/grease anything that needs it (will need to clean more often if you lubricate due to dust build up causing gunk)

Black-out curtains are great to stop light, but if it's entering the window already it's just heating up that one spot so you're still technically getting the thermal radiation. For that fix you would want reflective window covers, even foil would technically help slapped to the window (it's the only time those reflective insulation boards actually do anything with infrared). Foil with something behind it to insulate, like literally anything (cardboard wrapped in plastic to air seal can even do it), then you can take down your contraption at night to let air through to cool.

Insulating and air sealing. Alternatively, air flow in any spots building more heat than the outside temp (like an attic or upstairs area). If it's a family owned place it's easier, renting you might have to address concerns with landlord.

Currently temps in my area are getting about 95f(35c) daytime and 65f(18c) to 60f(15c) at night. I can usually get my house down to 68ish(20c) before the sun comes up. Windows in a bottom floor with fans pointing in, any windows upstairs with fans blowing out (hot air rises, it's the same technique for american colonial/victorian houses with dormers emulating ancient style architecture for passive cooling). If it's single story just be aware of wind direction if you're using the fan method and point some in where the wind is blowing and pointing out at the opposite side. My house will at max hit about 80f(26c) but by then it's time to open the windows because the sun has set.

At some point, once true-true summer hits, the nights will be about 80f(26c) and over 100f(38cish) during the day. At that point regulating your body and getting used to the temps is key and an A/C or sometype of ground thermal air flow is the only way you're going to make anything cool. If you're using A/C just seal the crap out of your windows with plastic and/or insulation (remember condensation like an ice cup though will cause moisture and mold/mildew growth on the exterior if not done properly). Pick a room that keeps the coldest and put whatever you can on the walls and windows (even a quilt on the walls will help insulate some). Seal up as much as possible and hide from the heat.