You can choose to send your calls to the phone of a colleague unconditionally, or in case of no answer.
In the “Incoming calls” section of your settings, in the “Call forwarding” line
Select the name of your colleague(s) for one of the options (no answer or unconditional).
Click the switch. It will turn green.
Your calls will be automatically forwarded to the selected colleague(s) according to your chosen option. Forwarded calls will appear in your call log.