This is actually a good place to start. We are after all worshipping God and God is beyond our understanding. In fact, if we could understand everything about him, we would be as clever as he is and he would no longer be God.
It follows, then, that we cannot expect to understand everything in the Bible. Although it contains guidance on how to live in the world today, it is mainly a collection of encounters with God in many different circumstances stretching over many centuries and cultures. Many of these encounters were mysterious events for the people involved and they are mysteries for us now.
The same applies to some of our traditional hymns and prayers. They are written in (to us) old-fashioned language and some of them are very rich in their references to scripture. We cannot expect to recognise and understand them all at once.
Does that mean we should drop them - or do we need to be taught what everything means before we can say it? No, definitely not. For two reasons - (1) it would be impossible anyway, as I have explained above; and (2) that would be to confuse the Church with a driving school. Obviously you need to learn the rules of the road and to have driving lessons before you can take a car on the road. But the Christian faith is not like that. You learn it as you go along and, importantly, as you make mistakes.
The thing is, when you repeat words and phrases from the service, they get tucked away in your mind. Then one day, when you hear something or you are in a certain situation, they will pop out again and make sense.
Peter