Something I found interesting about the relationship ship between English and German is that native German speakers often have an easier time reading Old English then native English speakers.

This is with no prior knowledge of Old English, of course.

German and English are also both germanic languages and they have a lot of common vocabulary.

As a native German speaker who had to learn the English language, I think that effect to be overrated.

Many of the English words with common German roots have parted ways so profoundly by now, they are often hardly recognizable as the same word any more (doesn't help that the Germanic base was some version of Plattdeutsch spoken in the northern part of Lower Saxony and the Netherlands, which many Germans also don't really understand).

The words that actually were surprisingly easy to understand for me, are the ones with common Latin (or maybe French) roots.

That is one of the reasons many Germans tend to sound presumptuous to native speakers, as they are more likely to use those often more formal expressions.

I'd be careful in regards to the similar vocabulary. There are many false friends. For example, you'd get very different things if you got a 'Gift' in Germany and a 'gift' in England.