You don't have to consciously and rationally understand the grammar - you didn't when first learning to speak your first language!
Stephen Krashen is a pretty good researcher on this - the summary is that exposure to the language for time (e.g. 500 hours of content you just about understand) is the critical factor. This is training non-conscious parts of your brain's neural network.
Some people like understanding the grammar and structure of a language consciously, and it can help as a mnemonic aid for anyone. But it isn't necessary, or the critical process.