If you can afford the money, then taking lessons will help you faster than language exchanges for a very simple reason. In a one hour paid lesson, you spend one hour working on your target language. In a one hour language exchange, you spend only half an hour on your target language.

Im a Japanese community teacher. I spend 1or 2hours for each lesson preparation to give the best service. For example, I prepare asking sentences based on their Japanese level and their interests. In Japan, education business is a service business like hotel business. Because, there are so many private schools and they compete seriously.

you should aim to have regular one-hour lessons with a professional teacher, who has uploaded their certificates, who can also speak your native language fluently(although it may not always be fully native). If you spend an hour speaking your target language, it will benefit you more than one hour with language exchange partner, because the language exchange person will constantly want you to help them with their learning of your language. there are also good community teachers on Italki who will also force you to use your target language.

I think having a tutor and a language partner are both helpful, but when you have a tutor you get to spend 100% of the time in your target language and it always fits into your schedule.

Taking lessons with community tutors and writing notebook entries have helped me a lot.