Lookup fields in Salesforce won’t sync as you’re hoping to HubSpot. Lookups will need to be synced as picklist fields in HubSpot. For example, if you’re using a User Lookup in Salesforce, a property needs to be created in HubSpot with the User’s name as the field value and the Salesforce User ID as the API value. If you’re looking up an Account or Contact, there will be too many values for this to be a sustainable method. Typically, I don’t recommend syncing Lookup fields between the two.