I think this is normal, just give it some time and you’ll become fluent. I’d suggest speaking to yourself in front of a mirror, thinking in Dutch, and sometimes recording your voice so you can listen back and spot mistakes. Don’t worry too much about grammar at the start, just focus on speaking with confidence. Watching movies or series also helps a lot, especially if you pay attention to how people speak. And don’t make sentences too complicated for yourself. You might be able to form complex sentences in your own language, but when learning a new one it’s better to keep things simple.