We will only receive the inbound messages in the Conversation tab using Highlevel's mobile app and web app.
Incoming SMS will not be forwarded to the forwarding number
You set up a Customer replied workflow trigger like this with the Custom Value {{message.body}}

Click on Automation > Workflows > Create workflow






Choose Start from scratch


Click on Create new workflow






Click on Add New Workflow Trigger







Click on Customer Replied




Click on Add filters





Select Reply channel


In the reply channel dropdown, choose SMS





Click on Save Trigger


Click on Add your first Action



Click on Send Internal Notification






Note: SMS notification will create charges for every sms sent



Click on Custom Values > MessageMessage Body





Click on Contact > First Name