'Singular they' has been correct English grammar since around the 12th century, I believe (definitely have read 12th somewhere quite recently, can't find it now, so I'll go with 14th). It was only in the Victorian era, from what I've gathered, that 'genderless he' became 'the correct way' (until that point, *both* were 'correct' when discussing an unknown person/person of unknown gender). In other words, 'singular they' is significantly older than 'singular you' and both predate 'only genderless he is correct'. Most people will naturally default to 'singular they' when discussing someone unknown, I have rarely heard someone say 'someone has lost his umbrella', for example, unless in a context (such as an all boys' school) where it could *only* be a 'he', most people would say 'someone has lost their umbrella', or avoid the pronoun altogether and use an article.
One way to look at the verb issue is 'speaks is 3rd person singular, speak is 3rd person plural'. Another way to look at it is 'speaks applies to "he" or "she", 'speak' is for literally every other pronoun.' 'Speak' is clearly not an exclusively plural form of the verb, because it is perfectly valid when used for 'I speak' or 'you speak'.
(The Victorians are also responsible for such grammatical nonsenses as 'you mustn't split infinitives because you can't do that in Latin [where they are single words]', because they were *really* into prescriptivist attitudes to grammar, personally, I prefer a more descriptivist, flexible approach, because language evolves as times change. (That is to say, the 'genderless he' was not a reflection of an organic change in the language, but a decision made by Some Person Writing A Book On Grammar, pretty much.))
Ultimately, if it's good enough for Austen, Byron, Chaucer, and Defoe, it's good enough for me.
As for the original question, my gut feeling is that the errors are intentional, because they look less like errors someone translating hurriedly from German would make than they do errors that someone perhaps not too familiar with what badly-written English tends to look like would intentionally put in, if you see what I mean? I feel like the first would look more like perhaps "We believe Nessah in a small cave west from here hides. Go there, kill she, then come to me back" (closer to German sentence structure, most people are more likely to mess that up than spelling, IME), and probably if *I* were writing an 'error-filled' version I might make it more like "We beleve that Nessah is hid in a small cave west of here. Go their, kill her, than come back to me," or something along those lines. (Mind you, I missed urst's point that the German versions don't have errors, so maybe I'm talking out of somewhere south of my face...)