Two keys from one one model

class sale(models.Model):
buyer = models.CharField(max_length=30)
item = models.ForeignKey(product,on_delete=models.CASCADE)
phone=models.PositiveIntegerField()
stockavailable= models.ForeignKey(product, related_name=‘numberofitem’,on_delete=models.CASCADE)
quantity=models.PositiveIntegerField()
email=models.EmailField()
available = models.BooleanField(default=True)

class product(models.Model):
category = models.ForeignKey(Category,related_name=‘products’,on_delete=models.CASCADE)
name = models.CharField(max_length = 200)
description = models.TextField(blank=True)
storelocation = models.CharField(max_length = 200, blank =True)
numberofitem = models.PositiveIntegerField()
sales.sale.stockavailable: (fields.E302) Reverse accessor for ‘sale.stockavailable’ clashes with field name ‘product.numberofitem’.
HINT: Rename field ‘product.numberofitem’, or add/change a related_name argument to the definition for field ‘sale.stockavailable’.
sales.sale.stockavailable: (fields.E303) Reverse query name for ‘sale.stockavailable’ clashes with field name ‘product.numberofitem’.
HINT: Rename field ‘product.numberofitem’, or add/change a related_name argument to the definition for field ‘sale.stockavailable’.
How do i access numberofitem from stock in sales?