hi Ibrahim,
Unfortunately you are not alone in an industry that in general is more interested in selling you the latest “story” than it is in educating you about the best possible choice of a mattress that will best suit your needs and preferences. There are many in the industry that will do a great job of guiding and helping you but unfortunately thay are usually overwhelmed in the “noise” of the advertising that most people are exposed to by the major brands and mass market outlets. In general you will do better by first finding the “experts” in your area than you will by trying to choose a mattress in the absence of meaningful information that can help you make meaningful comparisons.
There are some step by step guidelines post #10 here that can greatly improve your odds of ending up with a high quality, more durable, and much better value mattress no matter what your budget may be.
There are three basic categories of foam which are memory foam, polyfoam, and latex. Of these three … memory foam tends to be the most insulating and warmest, polyfoam is in the middle, and latex is the coolest. There are cooler and warmer versions in each category but this will give you a general idea of which foams are the coolest. There is more about the many factors involved in regulating sleeping temperature (which either add to or take away from each other) in post #2 here.
As long as you know the pros and cons of each then there is no wrong or right and it’s really a matter of personal preferences. There’s more about the pros and cons of memory foam here and the pros and cons of latex here.
If you let me know your city or zip I’ll be happy to let you know of any local manufacturers or retailers that may make or sell them that I’m aware of in your area.
With latex … depending on the other cooling components in your mattress and bedding … not much. With memory foam it depends on the factors in the link about sleeping temperatures. There are also many methods of cooling down memory foam and there is more information about this in post #6 here.
The mattresses section of the site and the more detailed pages in each of the subsections includes general and some more specific guidelines for different body types, sleeping positions, and how different layering combinations can affect both of these. In general though, mattress theory and design can be very complex (and frustrating) and there are many variables that are unique to each person so it’s normally most effective to just scan the overviews so you can ask better questions and then to “find” the experts instead becoming one yourself and using specs to choose a mattress instead of personal testing in a showroom.
This is plenty to find a great mattress that uses the best quality materials 
Phoenix