you need to inherit the model of 'crm.lead' first

after that, let's get into business

regarding the 'company_id',
override the default fields by rewriting them in your inherit model
then add a 'default' attribute to fill the corresponding field with a pre-determined value

as for example:
company_id = fields.Many2one('res.company', string='Company', default=lambda self: self.env.company)

there we try getting the currently active company as the default value for 'company_id'

same goes to the 'team_id',
but for this case, it depends on you which record you want to set as the default value, because there is nothing like 'self.env.team'

as for example:
team_id = fields.Many2one('crm.team', string='Sales Team', default=lambda self: self.env['crm.team'].search([], limit=1))

Hope it helps,
please correct me if I did any mistake!