SI'm sitting at the familiarmy usual café right now,. I'm going to have an appointment with K this afternoon.

My head isI feel a bit dizzy, because of the enormous amount of coffee I drank.

But I skipped my daily routine this morning to go to theon a rendezvous -/date at our preferred café.

It's so damn good; I canould clearly smell the cinnamon scent in the air.

After the first sip, my mouth iwas filled with a pleasant, light sweetness.

There are also fruity flavors to the bean, which is something I really enjoy.

Or : The bean also had some fruity flavours which I love.

I told him to try thehave a taste of it as well.

Then I went to a table upstairs and did my jobsome work.

He said they were bonus or m the house; thanking me for asking him to grind the beans, and also because he realized that the grinder had ground the beans the wrong size.

Wow he's thanking you for asking him to help you 😯what a nice barista! 😌

My head is a bit dizzy, because of the enormous amount of coffee I drank.

There are also fruity flavors to the bean, which is something I really enjoy.

I told him to try the taste of it as well.

"Try it" already implies tasting it. Also sounds more natural this way

Then I went to a table upstairs and did my jobwork.

Fifty minutes later, he came up and gave me two more coffee bottles, one was also "Coffee de Olla" and the other was(one) was made from my beans.

He said they were a bonus for me; t. Thanking me fors to me asking him to grind the beans, he realized that the grinder had groundwas in the wrong grind size.

Added "thanks to me,..." to make the sentence more connected.

I think the latter half is what you mean. I don't know anything about coffee grinding.

My head isI feel a blittle dizzy, because of the enormous amount ofhow much coffee I drank.

We would say that we feel dizzy, not that our head feels dizzy.
The comma is unnecessary.
While not technically incorrect, we usually wouldn't say something like "enormous" or "large", we use "how much" in these situations.

I usually make my coffee at home with a Vietnamese filter - the Phin - a stainless steel tool that I use for brewing my coffeecalled the Phin.

The explanation at the end isn't necessary, we know it's used for making coffee from "make my coffee at home".

But today I skipped my dailymorning routine this morning to go to theour rendezvous - our preferredthe café.

I switched a couple things around for clarity.
Added "today" to the beginning to better show that today's an exception to the norm.
Made daily routine into morning routine since we haven't been through the entire day yet.

Today I chose a signature called "Coffee de Olla", made with El Salvadoran coffee beans, cinnamon, and a special kind of South American sugar whose name I forget.

Salvadoran is the correct demonym.

After tThe first sip, filled my mouth is filled with a pleasant, light sweetness.

It's more clear to use more active voice here.

There are also fruity flavors to the bean, which is something I really enjoy.

Fixed typo with not having "I" there.

By the way,I forgot to mention it, but I asked the barista to help me grind the pack of beans that M. gave me.

"I forgot to mention it" is a more natural expression here.

I told him to try the taste of it as well.

"the taste of" isn't necessary since he'll already be tasting it when trying it.

Then I went to a table upstairs and did my jobwork.

We would use "work" here since it sounds like you're working on things for your job at the café.

Fifty minutes later, the barista came up and gave me two more coffee bottles, one was alsothe "Coffee de Olla" and the other was fromone of my beans.

Replace "also" with "the" since it's the first item in the list and we're familiar with it from before. We should also specify that it's the barista for clarity.

He said they were a bonus for me; thanking me for asking him to grind the beans, he realized that the grinder had ground the wrong size.

If the beans were damaged in that process then it'd be more of an apologetic gesture than a thankful one, I'm not sure exactly what that last part is saying though.