a "picture" is not going to prove anything. you have to ask him to send the "transaction ID" of the transaction he claims he has sent to you. it is going to be in hexadecimal format with 64 characters. you can then check if you can see that ID in your wallet (history tab) or not. you can also search it in a block explorer. and it would look something like this (a random example i chose from the recent blocks):
https://blockchair.com/bitcoin/transaction/06053bd50ee8f8269dc3c24aca0e9b9f2267a038fa33a37802e8a4a4a038bc4f
1) this status tells you if the tx is confirmed (is included in a block and final or is in the mempool and not-final) https://bitcoin.stackexchange.com/q/146/87716
2) a list of receiving addresses where you must find your own address to be one of them
3) the corresponding amount of bitcoin that went to each address which must be the same amount that you expected