I have the problem that my computer often (several times per hour) suddenly disconnects from wifi. Then I have to disable and enable the wireless connection so the network I disconnected from is available again.
I wondered that something must be wrong with my wireless card (AWUS036H) so I investigated how to install a proper driver and found this. However, when I open a terminal as root and follow the instructions (sudo make), it outputs this.
I use Debian Jessie with 3.16.0-4-amd64 kernel. I have build essential and linux-headers-3.16.0-4-amd64 installed.
The Realtek download page that you link to describes the available driver as
Linux driver for Kernel 3.0.0/3.1.0/3.2.0
You have a much more recent kernel (3.16), so the kernel headers have changed significantly, and compiling fails.
However, the direct-from-Realtek driver probably won't help. It was last updated in 2012 (to support kernel 3.x). The same source files were included in the "staging" area of the kernel where they were maintained for a few years. (See the changelog). That directory was deleted in 2014 with the following explanation:
There is a "real" driver for this hardware now in drivers/net/ so remove the staging version as it's not needed anymore.
That means that the kernel developers consider the stock driver, that you were already using, to be more suitable than the old one you've downloaded and are trying to compile. And even if you wanted to use the old one, you'd be more successful trying to compile the last
As commenters have mentioned, it's more likely the hardware that's the problem.