Hi,

You have to find the next stage from the crm.stage model and get its id and then set the stage_id field in the crm.lead model.

Suppose if you need to move it the stage with name "Qualified", you can get the id of stage Qualified as follow,

stage_id = self.env['crm.stage'].search([('name', '=', 'Qualified')], limit=1)

Then,

def onchangecountq(self):

if self.quotation_count >0:

stage_id = self.env['crm.stage'].search([('name', '=', 'Qualified')], limit=1)
self.stage_id= stage_id.id

Thanks