Critique of Zolkabro's My Life as an Earthling
I feel like the introduction is far too choppy and factual to really bring in readers. I'd add in more description, more personal details, and a hook to really bring readers in. Even aliens need to sell their books to scanning customers. Also, did you think about jet lag? It may not apply, but it could be something to think about.

I think that aliens would find 'bread' a strangely cooked grain, and i feel that the author would comment on that, rather than the sanctity of bread.
I saw that my tentacle was now dry as bone, but safe.
This doesn't really flow. Something more like "My tentacle dried up on contact, but fortunately was not hurt by the acid."
Also, I don't think the alien would be foolhardy enough to just drink the tea if he can feel how hot it is. He would just notice the heat by touch, and then look it up.
writing it slowly and deliberately, and very messy.
If he was writing slowly and deliberately, he would think it was just plain messy. However, it could certainly be messy compared to the hotel owner's handwriting.

For the pub, I'd mention how quickly he drank the beer. If he drank it slowly, most humans would not really be expecting much. If he drank them quickly in close succession, most humans would expect him to get drunk. Also, I'd be surprised if humans didn't encourage him to try a variety to alcoholic beverages, and maybe try to get him to have a big glass of a strong liquor, just to see his reaction. If they wanted to make fun of him when he got drunk, then that behavior would fit in perfectly. Also, he would have done little that day before going to the pub, mentioning it after disrupts the temporal progression.

I can't help but think it odd that Gronkle's species has a non-verbal language, yet he can learn to speak french. Also, if the author can't eat human food, what has he been living off of? He would be very uncomfortably if all the food he had was inedible hotel food to eat for almost three days.

Why does it take the author so long to go see the tourist attractions? If he is vacationing on Earth, and he is uncomfortable with the food and the people, he is obviously not going there to relax. Therefore he would want to go see the sights, and according to his diary, he doesn't do much the first four days. Spending one day on the sights is really a waste of almost a week in a strange world. Also, I feel that extra-terrestrial would be the politically correct term for visitors from other planets, and that alien would only be used in a derogatory way (like other scientific terms that have become insulting to certain groups).

At the end, there is a sudden change of heart from the author. He has spent five days complaining about humans, and then suddenly he accepts them. What brought about this change? It should definitely show in the journal his gradual acceptance for the people of planet Earth. The author also has a very human social instinct, hesitating and fleeing from uncomfortable conversations. Is this intentional?

I hope this helps you.