According to Link2SD I only have 2% system space left

System space is internal andoid space (not your SD card/storage space). To make more empty space available in your system, you can do the following:

• Clean system cache (there are various apps to do that);
• Uninstall unused apps;
• Move apps to sd card (with App2SD or similar application);

System space depends on the device and is limited amount of space which contains your ROM, system and applications. It is not good if it has only 2% space left as your device might become slow or cause some apps to crash.