Is there a way to use the timer without using Wifi connection to Phone?
There is, and you should find it in the Quick Start Guide or the FAQ section of the Support page. Try here.
But really, you’re better off not using the onboard timer. It’s really just an annoyance. For most sous vide processing time is flexible, an extra half hour to 2 hours is not going to make much difference. For things that are time critical, like fish and other seafood you’re better off using a standalone timer that you can carry around with you. The timer on the device is only there because people seem to think it needs a timer.
Nice simple video https://www.youtube.com/watch?v=kMTlET527J8