Whatsapp Message

I have prepared an excel sheet from where I want to send WhatsApp messages. The link of the same is

https://birlaedu-my.sharepoint.com/:x:/g/personal/bps020406_atlas_betpilani_org/EX0NaaLMXXFGl7OUA0HUdrgBbzJX1NKtDLVpTHp2kK2JJA?e=1UkRvj

When I want to increase the length of the sentence I am getting an error. please refer to cell 'T13' of the sheet.

please help to resolve the problem

regards