It's natural to make errors when learning, but the errors in your text tell me that you are quite careless with English. Your best plan is to revise what you already know and make sure you can understand and use your current knowledge perfectly.
I'm not sure how you managed to count the words in your vocabulary, and I'm confused as to whether you mean "fifteen thousand" (15,000) or "fifty thousand" (50,000).
Pay more attention when listening, writing, reading and speaking, and do so consciously. The improvements you make in each area will make your English ability much stronger.