I wake up at 7am, but if I gethave trouble with sleep ing that night, I will sleep in for a bita bit longer.

"I wake up at" means it is your usual routine, and the "but" is required to show when/why you have deviations from that routine on any particular night (that night). "I will sleep in" is not wrong, but to "sleep in" tends to be a guilty treat, to sleep longer than we actually need to.

I takedrink a little water, brush my teeth, and take a quick cold shower.

"Take" in terms of food or drink will always mean to physically take it into your hands (only! not drinking or eating it). Example: We went hiking, so I took my bottle of water with me.

I take a walk, stroll downing around my apartment building.

You can use "stroll/walk down" when it can be envisioned as a straight pathway. Stroll down a street, a hallway, a trail, a path, etc. If it is to describe walking in a general area (inside a building, a neighborhood, a park), use "around."

Then I go back into my apartment... to take another cold shower again, because it's hot as hell.

"Into" isn't used to mean returning to one's home. "To take a cold shower again" isn't wrong, but "another shower" is more natural in my opinion. An additional quantity of X = another X, which works for showers because we can say that we "have a shower."

Then I have a breakfast,. I eat very few or some days I don't eat at alllittle, or not at all on some days.

"Few" is for things that can be discretely counted (a few apples, minutes), and "little" is for things that either can't be counted or would be really difficult to count or are considered in the general sense (a little sand, time).

After finishing, I enter eating, I go in my room, open my laptop, plan my day and start doing my tasks for mythat day.

"I enter my room" is not wrong, it is just very factual/impersonal and doesn't fit the rest of your style of this text.

I wake up at 7am, i. If I gethad trouble with sleep athe night before, I will sleep in for a bit.

I take a littldrink some water, brush my teeth, and take a quick cold shower.

I take a walk, strolling down around my apartment building.

Then I go back into my apartment... to take a cold shower again, because it's hot as hell.

I have a breakfast,. I eat very fewlittle, or some days, I don't eat at all.

After finishing, I enter my room, open my laptop, plan my day, and start doingmy tasks for mythe day.