Paper plate business loss by family relative

Hi, One of my family relative approached me for starting a business. But not planned which business to start with. I told I can only do investment and not take responsibility of the business. It will be your responsibility to run business and share profit with me. Please note no bond or contract was made. It was all oral communication since he was a family member. Then he and his friend decided to do paper plate business and they asked me to get one. I found best offer online and bought for them (machine was registered in my relative name not mine) but money was paid by me. Like wise given money for the business setup. Intially they said we will get you profit out of it don't worry but now they are saying business isn't working what ever you invested we have spent it for business and they have their own calculations which I may not trust as they don't have receipts for those expenses. So now I have all the transactions made to my family relative and the whatsapp chat screenshots as a proof. And in the chat I specifically mentioned it was your idea to start paper plate business. For that they acknowledge. Could you please guide how can I take legal actions without having written contract but with having above proofs? I am expecting full return of money around Rs4.2lac as it was not my fault. Kindly share me your thoughts. Thanks.