Try not to translate when learning the Polish vocabulary. Try to associate objects or actions directly with their Polish name. This makes a stronger association and the vocabulary is permanently assimilated much more quickly. Of course there is science involved in learning languages, but there is also an art to it. Some things you may not understand immediately, it would be remarkable if you understood everything at once. Go with the flow. If you are talking, use the words that you know. Do not worry about that word you have forgotten or have not yet come across. Make the most of the moment -- communicate.
Language is spontaneous by nature; adults speaking their own language often make mistakes. You should not be discouraged by the mistakes that you make, you should concentrate more on what you have achieved. Of course it is important to correct mistakes and reduce their frequency; but when you have the opportunity to speak Polish to someone - make the most of it - talk, say what you want to say. If you use the words that you do know as stepping-stones, it does not matter, this is normal. As you continue the gaps between the stones will become filled up with new vocabulary.
It is necessary to accept that for the moment and for some time, you will not have the adult command of language that you have in English; this is a temporary frustration. The important thing is that you do not allow it to frustrate your efforts.
Sometimes it is helpful to write down short word lists. This is because one of the penalties of literacy is that in time hearing is often insufficient, one needs to write it down.
This is an acknowledgement of fact, it doe not diminish the importance of not translating. Assuming that you do not plan to become a translator, then you should not translate. Plunge into the language; try to learn the way a child learns. Children learn by associating a sound with an object or an experience and then identifying the sounds with symbols.
If one considers all the other things that a child must learn, it seems that they make good progress using their method of language acquisition. They are not inhibited they just do it and speak. This is the attitude that brings success; this is the attitude that breaks through the barrier. The time for refinement will come later. Now go for it; listen to it, talk it, read it and then write it. Listen to people speaking, or a watch a film with the sound in Polish and then repeat it a few times. When learning a science such as physics or chemistry, it is important to understand every step of the process, because it is logic based and consequential. This is not so with any language, few would say that English grammar or spelling is logical or consequential. You learned English by being surrounded with it and participating. Go for it, speak it, the more you do it the better it becomes.
Sometimes the best way of learning the language is through visiting various forums and interacting with people. If you are a foreigner living in Poland or just want to learn more about the Polish culture and people, you may visit a forum about Poland for English-speakers.