The letters with umlauts are lowercase letters.
There aren't any uppercase letters with them, or any lowercase letters without them, so perhaps the umlauts were just to make clear that this was a lowercase letter.The Landers were a Slave Race to the race who left the messages.
The guy writing the Apocalyptic Log in the beginning seems to be the last survivor of his race, so it's not likely the Landers were other members. Besides, the Landers speak in a very friendly tone, while the messages are more formal yet less polite and in some cases even somewhat trollish. This would explain all that completely. It's more likely Slave Race than Servant Race because an enslaved race would be less likely to sacrifice themselves entirely for their masters than a specially engineered race.The "chips" are batteries.
Many of them are needed to power the main cannon (which has limited capacity), but the Landers can use them as the power source for sub-weapons (which, logically, have a limited power supply, fitting with how they're one-time purchases).