I agree with Eden's comment about context but also remember that you can probably LEARN about 500 words a year if you have one or two lessons a week.
When you start learning another language you learn perhaps 8 words in the first lesson ( perhaps "Hello, my name is .... I am .... years old" in English). You go home and think 'Fantastic! I've learnt 8 words.' - you go to the next lesson and remember most of them. Okay, so maybe you don't know them all but you are learning 8 words. You only make two or three mistakes and therefore you feel good.
But many psychologists say that on average we need to see/use a word about 8 or 9 times (some say between 4 and 40 times!).
So how many words are you learning at lower intermediate level? Thousands...
How many mistakes do you make? Hundreds
You don't feel so good.
I think most students can relax a little, be patient and realise that making repeated mistakes - and repeatedly not quite remembering words (and needing a prompt from a friend or a teacher or looking it up in a dictionary) is all part of the process of learning. Read, listen, watch films, write and talk in the language, and eventually, slowly, slowly, those words will become part of your usable vocabulary.