Upvote:1
For Romance languages there is more German influence on the grammar than the vocabulary.
Wikipedia on the history of the development of Vulgar Latin (which led to the Romance languages):
What emerged in Western Europe was a common form of Latin which, though mostly Latin in vocabulary (with many Germanic words introduced), was heavily influenced by Germanic grammar and represented a radical shift away from the original Roman language. For a few centuries this language remained relatively common across most of Western Europe (hence the fact that Italian, Spanish, French, etc. are far more similar to each other than to Classical Latin), though regional dialects were already developing...
Upvote:5
This topic is described in detail in Empires of the Word: A Language History of the World by Nicholas Ostler. It includes references to his sources.
Short version: relatively little, and we're not really sure why. Germanic Tribes were mostly assimilated wherever they settled.
The only exception is England - most likely due to the plague wiping out everyone else.
https://www.goodreads.com/book/show/166433.Empires_of_the_Word