Are there shutters? Are you allowed to install any?

I'd use Thermal curtains that you can close during the summer days and leave open during the winter to let the sun heat the apartment. JCPenny's carries them for a reasonable price. I use both blinds and curtains.

Solar shades cut down the heat quite a bit, and they don't block the view. Easy to pull up and down. Get a valance if you order them. The entire thing hides under the valance.

We have West sun on our dining room, and they work great. We chose off white, but have black in our media room, and the view is easier to see through the black.

Are you still going to be living in the Netherlands?
www.protectsun.eu/
www.hollandinteriors.com/product/
The thermal curtains sound like a good solution as well. I understand humidity is a big problem. Would a small fan to circulate air be of any help?

The two places noted above advertise blinds and shutters. You might want to check with them and if they are out of your price range, perhaps a friend can give you the name of someone who is cheaper and does quality work.

get either a vintage (on eBay) or a Bionaire dual-fan window fan and put both fans on exhaust so that it pulls the hot air out of the apartment.

If you can open two windows on opposite sides of the apartment, with the fan exhaustion air in one of them, that will dramatically cool the apartment down.

Venetian blinds will block the light but let the air circulate.

If you can place a small air conditioner in one window and a narrow window fan venting out in another window on the opposite side of the apartment (possibly in the bathroom, or if you have a good bathroom vent that might suffice) you can have cool air wafting through most of the apartment. BJ's has been selling new narrower window fans that are only about 6 inches high that are fairly powerful and have three little fans in them that can be adjusted for air flow.

Make certain at least one window can take an air conditioner, and has a three prong, grounded plug under it--insist the renter install one if not.

Clip on fans are also a great help as long as they are within about three feet of wherever you are sitting or standing, and they take little space.

I have a window that lets in outrageous amounts of heat in the summertime. I have sheers in a lace design at the top with a valance of heavy fabric over that which only allows three to four inches (bottom of valance is scalloped) of the sheer to show.

The bottom of this window I have covered in cafe curtains made of heavy, decorative bath towels folded double and
hung with clip on cafe curtain rings. Also in the bottom is the small air conditioner. I keep the cafe curtains drawn to the sides of the air conditioner when it is going, but they can be drawn shut when the ac is off or it is cold out. I shopped for curtains that would do what I wanted in this window for years before giving up and creating my own solution, which works really well and is fairly attractive, as I was able to find a sale valance in a basic color and sale bath towels in an interesting, matching pattern.

I presently have two fans venting out--one in my bathroom, with narrow Venetian blinds pulled down to the top of the fan.

The other out-venting fan is in my kitchen, installed there while I await workers to install a new stove vent. The cafe curtains I have in the kitchen window are easy to move aside to allow the fan to work properly.

In my livingroom, I previously had shutters at the top of the three side-by- side windows above our enormous picture window setup, but they were a maintenance nightmare. I now have three sheers in a heavy lace design up there and they seem to insulate from heat and cold just as well as the shutters did.

I have the picture window/s on the bottom covered by three sets of thermal drapes, hung on a rod with pin-on rings.

Unless you hate sun, I recommend you try sheers first, and then add more opaque thermals to cover those as needed. That would require double rods at the tops of your windows. In more informal areas, you may find cafe curtains would suffice.

Venetian blinds are also wonderful in situations like yours, and you have almost infinite control of heat and light with them. In the heat of the day you can turn them upward so that sun bounces off each blind, giving the light that enters a soft, diffused quality but blocking most of the heat. You can use them alone, which gives a light, airy effect, or with thermal drapes to pull over them.