I don't think you CAN do much different. Learning a language simply takes time. It also depends on the age of your students how easily they learn the language and how fast they can absorb new vocabulary. Not every child/person can read a word and then know it in their heads forever...leaving grammar aside, even.
I teach English in Germany. We start teaching English to our kids at elementary school now (age 6). Until recently we have started at the age of 10. And at the end of the school year students were able to hold very simple conversations such as: Hello, my name is...Where are you from?...I'm from... How do you do? and so forth. I start using the English language as constant class room language only half way through the second or even after the second year of English learning. Sometimes you still have to go back to using your native language to explain difficult grammar issues in the third or fourth year of learning.
Languages are complicated. And even if the grammar - at first glance - seems easy in English (at least easier than German with all its different cases) there are a lot of hidden problems when it comes to the use of words in different contexts where one word can have very different meanings, or the use of prepositions in certain contexts, and alike.
Just be patient.