Why the date it arrived matters more than you think
Repair obligations run from when you were told. If the record of being told is a WhatsApp message you have since scrolled past, you cannot show when the clock started, and that is the single fact every disrepair argument turns on.
A request from the portal is dated the moment it arrives, without either side having to do anything.
Contractors
Keep your own register of who you use, with their trades and contact details. Assign one to a job and the work sits against the property with the cost, so the repairs history builds itself rather than being reconstructed at tax time.
Closing the loop
Reply from the same place. The tenant sees the response in their portal, and you have a record that you answered, when, and what you said.