Being a Newbie Architect - Day 6

Since “newbie architect” is a role you’re fulfilling, you should use it as a noun. “A” is never capitalised in titles, so we don’t do that here.

A few days previously, I complained in my writing In my writing a few days before, I complained about my first client.

“Previous” is too clunky to be used in a compound sentence. We generally don’t use it to refer to dates/events that had happened in the past. I believe making the “writing I did a few days before” the primary focus of your sentence (placing it at the forefront) balances everything better.

Anyway, I am a newbie architect who started my own company.

Since you own the company, it is yours. Therefore it is “my own company”.

For now there isn't any solid outcome yet, but I don't want to lose my hope.

In colloquial English we generally prefer missing out the possessive pronoun in the sentence “to lose hope”. It can clearly be inferred that the hope is yours in this sentence.

The working hours are up to me, not . Unsurprisingly, I am not that working that hard.

“Unsurprisingly” is a difficult word to use in a single compound sentence without running into issues with commas. You should generally start sentences with “unsurprisingly”, or surround it in commas “he was, unsurprisingly, lazy”.
The second sentence can either be interpreted as “I’m not working so much” or “I’m not that much of a hard worker”. I interpreted it as the first, so you should use “that” as an intensifier in this sentence.

Currently, I have a just 2 small project;s: one house and one apartment.

“A” shouldn’t ever come before “just” unless you are using “just” in the sense of talking about justice, or the judicial system. You shouldn’t use a semicolon here. Most English speakers don’t even know how to use a semicolon, so you should avoid it like the plague.

If it wasn't for my father and uncle, I would have already dropped this project.

This is a conditional phrase. Most conditional phrases require a logical conclusion that follows directly from the condition set. “If [x] hadn’t happened, I would be [y]”. We use “would have” because it’s something you wanted to do in the past, so you “would” have done it if not for your father and uncle.

In the endOverall, it hasn't been that long tosince I started to work so I don't know really know whether I like it or not.

“In the end” shouldn’t be used here, because your career hasn’t ended yet. I understand you wanted to refer to the end of your paragraph, but it would be incorrect to do so. We are still on the subject of your job and profession, not the letter you’re writing.
We add “since” before “I start” and change “start” to “started” because you have already begun your job, and you “started” in the past.
We put “really” before “know” instead of after. It’s technically correct in spoken English to say “I don’t know, really,” but in written English you need to surround the “really” with commas. It can get annoying to do this, so just try to avoid writing it as much as possible.