Hi nickela,
You can see some of my thoughts on the TempFlow mattresses in post #9 here. A forum search on “tempflow” (you can click this) will bring up more posts about them.
Some of the better quality/value online memory foam options I’m aware of are listed in post #12 here.
Oeko-Tex is a certification for harmful ingredients and offgassing that is more commonly seen with latex. For memory foam the most common certification is CertiPur (which has very similar testing protocols). You can see the guidelines I use for memory foam mattresses in post #10 here. One of these its that the memory foam and polyfoam in the mattress is either CertiPur certified or at least made by a foam manufacturer in North America.
The best way I know to find your “perfect” mattress is in the post that is linked at the bottom of all my posts (and the links to other information that it contains as well).
As you will see I place a high value on finding the better local factory direct manufacturers or better sleep shops in your area and if you let me know the city or zip where you live I’d be happy to let you know of any of the better options or possibilities I’m aware of in your area.
Phoenix