If you mean "sou da ne" (そうだね。), it means "Yes, I agree". It's a casual Japanese phrase used when agreeing with a statement.
It is based off the Japanese expression "sou desu" (そうです。) which means “It is so” or “That’s right.”
Getting used to Japanese grammar can be a bit tricky because of the word order, which is Subject - Object - Verb. Great if you're used to other languages, such as German or Turkish which have similar word orders, but possibly a little confusing for English speakers unfamiliar with it. So, the verb is placed at the end, meaning a simple sentence like "I watch television" would be "I television watch". This also means that you have to be patient as until the speaker reaches the very last word of the sentence, you won't know whether they're coming or going, agreeing or disagreeing and so on!
The most obvious challenge is probably learning the characters, but unfortunately, there's no getting around them! However, if you want to stick to spoken Japanese and just learn the Romanised script, then it can be a lot easier than learning many other languages. There are no pronunciations or tones to remember and each syllable is given equal emphasis.
Here are more facts about the Japanese language shared by BBC.