The way presentd here is for you to evaluate your standard , to see how much progress you did in your grammar and language in general , but to improve you have to do effort ,you say you are not improving , but what do you do > are you applying any methods right now ,yet you are not improving ?? So i ll just recommend you some ways to improve ,and if you are applying any methods ,and not improving ,then you are not giving enough time or concentrating enough in what you are doing !
Some ways , would be " - reading at your own level of comprehension using dictionary to look up the words you don't know "
-watching movies , attending lectures, listening to music , any method to be able to hear the language spoken .
-Mixing with people who speak the language ,trying to apply what you know and make mistakes no problem , you can always ask others for the meaning of words .
-And then by using one of those methods to evaluate your improvement , that would make you feel and sense your progress ,which would encourage you to go on !
Good luck !