So… I have gone for brutal honesty rather than mindless praise in the hope that I might be able to help you grow. I have read the first two chapters, and have added some feedback on the first few paragraphs. These will probably already give you a bit of an idea what I mean when I say that your grammar needs some work. The most glaring mistake is the constant switch between past and present tense. Overall, I believe there’s a fun story here. It just needs some polishing. I wish you a lot of fun writing it.

“the science council”. Don’t forget the article.

Right so… I get what your aim is: you want your reader to get an idea of what the character looks like… but… to be brutally honest… this comes across as awkward and desperate. This is just one person’s opinion, but maybe try something a little more subtle.

Just for believability: no scientist is going to work without tying their hair back. You really don’t want hair in your face/experiments when you’re handling dangerous chemicals.

You keep using past tense in one paragraph, and present tense in another. Try to choose.

You started your sentence with ‘now’ twice in a row. Not necessarily wrong, but it doesn’t really sound good.

‘Various experiments’. Should be plural.

I assume you mean ‘bought for free’ and not ‘brought for free’.

Also ‘a gas mask’. Don’t forget the article.

Replace ’gets’ with ‘was’. But, since you’re choosing both past tense and first person narrative, it comes across as rather strange. Since it’s past tense, the protagonist already knows whether or not it was successful: try to rephrase in a way that acknowledges the fact that the protagonist knows what’s going to happen (it’s past tense, he’s telling us what happened), but still adds some expectations for your readers.

Not immediately grammatically incorrect, but placing ‘intensively’ before ‘staring’ instead at the end of your sentence, would work better for the rhythm.

I promised sincerity, and consequently I have been quite honest with my feedback. Maybe even a bit too honest. I hope you are not dissuaded from writing after reading what I have written here. Keep in mind: it’s just one person’s opinion. The premise is promising, but it fails to fully capture my attention. Don’t get me wrong: the idea itself is interesting, but I’m not really inclined to keep reading. First off, I couldn’t even get past the first few chapters. Almost every paragraph has a grammatical error or an odd word choice. It really withholds your reader from continuing. I have corrected them in the first half, but after a while it just got to be too much. The characters themselves are a bit flat. I have nearly no information on them. I know the brother is older, likes to care for his sister, and doesn’t know how to handle money. I would like to see some more personality. As your reader I long for uniqueness and texture. You can show this in speech as well as behaviour. When it comes to their surroundings, I am in the dark. I know they’re at a marketplace. Alright, what kind of marketplace? What do they sell beside fruits? What’s the atmosphere like? What region are they in? What kind of people are there? We could just as well at a marketplace in 14th century France as at a marketplace in Babylon in 2000 v.Chr. Overall, I do believe this story has some real potential. Just keep writing and keep on practicing. I wish you all the best!

I’m assuming you mean ‘patrol’ and not petrol (a light fuel oil that is obtained by distilling petroleum and used in internal combustion engines.) Patrol in itself is a weird word choice. It means to keep watch over an area, especially by guards or police walking or driving around at regular intervals. Are they guards? That wasn’t clear up till now… I tought they were civilians.

The ‘thus’ is a language register higher than the language register you’ve been using up till now. It comes across as far too formal and feels out of place with the rest of your text.

I hope you wish comes true. Add ‘s’

This comes across as a bit too much exposition. I get that you want to let your readers know what kind of danger these people are living under, but it comes across as very forced

Left my core in ’a’ quiver. This would be grammatically correct, but it’s still an odd phrase. Certaintly if it’s dialogue. It comes across as very wooden and unnatural.

Fill my stomach, or, quench my hunger. ‘Quench my empty stomach’ is a bit of a malaphor

Try to separate the paragraph when someone else is speaking (see my first paragraph comment)

To retaliate: to return like for like. especially : to get revenge. transitive verb. : to repay in kind. retaliate an injury. (According to Miriam Webster) You can see it doesn’t really fit. It’s not an enormous grammatical mistake, but it comes across as very odd and aggressive for your reader.