I know the feeling. I suggest using a monolingual dictionary. They're way better because they don't just give blank translations but explanation of words meanings. They usually provide examples as well. In addition they do help along with the mental imprint thingy.
It's actually придурок, but you wrote this one down right phonetically. Might I mention how funny it is that you included this word. I hope there is nothing to read between the lines there.
That's kind of obvious, isn't it? If you see a word for the first time, you can't have any mental imprint on it. You don't even have the slightest idea what it means. Again, I suggest you use a monolingual (Russian) dictionary for the new words you come across. An explanation rather than translation facilitates association and helps you avoid linking a foreign word to a specific word from your native language.
проигрывать means to lose (continuous action)
проиграть means to lose (completed action)
Уметь doesn't mean to know but rather "possess an ability or skill to do something", be able to, can (modal verb)
Знать means to have knowledge of something or how to do something
Узнать means to gain knowledge of something or how to do something
The logic with послышаться is sound but unfortunately the word itself shifts meaning from just "hear" in this form
послышаться - used when you're not sure if you really heard something or when you misheared something
E.g
- Вася, звонят! Иди открой дверь!
- Петя, нет там никого!
- Да? Ну значит мне послышалось (I wrongly heard someone ring the doorbell)
Another example is when you're in disbelief that somebody has said something. Usually something you don't like. It's like "You did not just say that!"
- Аня, ты полная дура!
- Что? Мне не послышалось?
Наибольше is mostly spoken variant of наиболее. It has correlation with most, sure. But this gets tricky very fast. Russians form comperative and superlative adjectives a bit differently.
A few examples:
Наиболее эффективным решением является предложение господина Волкова. Самым эффективным решением является предложение господина Волкова
Those two both mean "The most effective soultion is the one Mr. Volkov has suggested".
This is where it gets tricky. Those two Russian sentences might have a slightly different flavor to them.
The one with наиболее might mean that the most effective solution comes from a set of suggested/presented solutions. Wherein the one with самый means that this solution is the most effective of all possible solutions, even the ones that were not suggested/presented.
Самый большой is just the superlative of "big". Самая большая страна на земле. Самый большой парк etc...
P.S. Более is often used to form a comparative adjective. Более эффективным решением является предложение господина Волкова - A more effective soultion is the one Mr. Volkov has suggested.
Смысл vs значение.
Well, смысл is more about talking about the gist of something. Like смысл высказывания, смысл предложения etc. It is usually used when talking about complex things. Like a sentence. Значение is very close to смысл and can be mostly interchangable with смысл. However, when talking about singular things, we usually go for значение. Like a word.
However, you can also say смысл слова. There is nothing wrong with it. It's just that it might imply some deep hidden meaning of a said word, not just its mundane meaning everybody is aware of.