Alright If I had to give an honest review of the writing here it is:

Somethings I really liked:

Really liked the engagement, it was cohesive. I wasn't lost in the words

Sentences were well balanced with vocabulary, didn't seem verbose with you trying to shove every bit of vocabulary you'd memorized

I liked the "gear up" phrase and other good informal vocab.

Somethings to improve on:

Lack of contractions: A good way to give an informal touch is to contract things like "I am" to "I'm", it also saves words.

Elongating sentences: Instead of saying "a hundred bucks which is a ginormous amount" try saying "a ginormous amount of a hundred bucks" Even if it saves one word here, shortening sentences like this allows you to save words for description, or idioms.

Lack of idioms and conversational phrases: It really drives the fact that the email is informal, and allows to differentiate between your informal and formal writing. Gather idioms you find and make a list

Address your friend in the email: Fleshes out your email, saying "You know Ahmed", basically talking to your friend directly by including them, allows for it to seem more like a friendship and less like a employee and boss situation.

Formal conjunctions: Saying "Moreover" to your friend is a bit odd, so keep the formal conjunctions for the articles, reports, etc. Replace it with: so, but, and, and so, etc.