Old English was more mutually understandable with Old Norse than German and Dutch are today as I recall. Northern English dialects still show the influence of Old Norse on the English they spoke not just in location names but in vocabulary and some grammar. It’s been years since I studied this in grad school, so please take it with a grain of salt.
There’s a guy on YouTube who, among other things, makes language intelligibility videos. Here’s the one he did on how well German speakers can understand Old English
I am conversational in Norwegian (basically Danish in written form) and fluent in English (my native language) Dutch, when you figure out the pronunciation and do a bit of mental figuring, is about 40% for me. I know the gist of what is being written (less of what is being said).
So how much old English from Beowulf do you “get” when it is pronounced. Basically the English had forgotten how to read Old English and it was a Danish/Icelandic linguist who helped figure out the language again.