Student Course Invoice Relationship

In my LMS system. i need to build up "Invoice Module" , so i created this ER Diagram. https://snipboard.io/bTjFSV.jpg

Could you please check and give your ideas. Basically i want to keep all course assigned student's invoices ,transactions purchased items ,finally i want to check every student pay their course fee on time or not .

Actually I want to build up this table connections using Laravel Eloquent Relationships.

Please advise me .