Coffee

Kanako san, your sentences are well written and perfectly understandable.  I would like suggest a few grammatical edits [ ... ]:

For the first time in several months since I took a cup of coffee. [Kanako san, the order can be improved.  “I had a cup of coffee for the first time in several months”.  I also struggle with the Japanese use of ‘goro’ or ‘kara’ :).  In English, it is more common to say “it has been”.  Otherwise, in this sentence, you could also say: “it had been several months since I had a cup of coffee until today”]

Before I used to drink decaffeinated teas for good sleep. [This sentence is correct grammatically –it neds a comma “,” after before.  You could also say “In the past, I used to drink decaffeinated teas for a good sleep”

Since I needed to learn tastes of coffee for my works,I started to take it again [“Since I needed to learn about various tastes of coffee for my work, I started to drink coffee again” –Note that “take” a drink is not an English expression, you “have” a drink or simply “drink” something.  Your sentence is correct, but I wonder if you mean for this sentence to be in the past tense?  ‘Did you need to learn’ or do you need to learn now in the present?]

It helps me to wake me up in the morning. [Coffee helps me to wake up in the morning].  So from today I can take it only in the morning.  [“So starting today, I can only drink it in the morning”