I want to build an exchange website, where users can buy and sell ecurrencies

I want to build a very user friendly exchange website where users can buy and sell ecurrencies and cryptos. Example of ecurrencies are Skrill, neteller pm webmoney, PayPal, payeer, giftcards, Amazon etc. Examples of major Cryptos are btc, ethereum, Bitcoin cash, etc. The above list is not exhaustive, I should be able to publish any currency of my choice, and also to remove any currency that we are not offering at the moment. The idea of the site is, I will buy and sell to customers with a profit. For instance, I can publish on the site: we are buying skrills #370 per $1, and selling skrills for #400 per $1. Just an example. So, users can click buy or sell button and fill in their details so as to exchange their ecurrencies and cryptos with us. Our payments are always going to be in naira. Second part of this project is, I want merchants to be able to advertise their ecurrencies offerings too, incase there are some ecurrencies that we do not have at that moment. That way, users of the website can also trade with the registered merchants directly, but payments must be made through us, and we act as escrow protection between the merchant and the customer. Only after both parties are settled, then we release naira payment to the appropriate person. In this case, our escrow will only hold Naira in our custody, and when both parties are satisfied, then we release to the appropriate person. We want the process of releasing payments to our customers to be automated or semi-automated, whereby, we can just click a button for EACH completed transactions and the naira gets credited to the customer. When customers trade directly with any of our merchants, then we act as the escrow by keeping the naira, and we will also charge a fee for this, from the merchant. % Fee to be set by us, maybe, 2-5%. When a customer decided to trade with the registered merchants, he would simply send a trade request, which the merchant will confirm, and there will be back and forth communications between them, until naira payment is sent, which will be sent to us, and we keep in our custody until both of them are settled, then we release to the appropriate person, after taking our own fees. So, it's a complex loop of communication between merchant and the customers, and the admin too, because admin has to confirm to the respective parties too, as at when money has been sent for the ecurrencies, and urging the merchant or otherwise to send the product to the customer, and customer has to confirm that he has received it, before admin will release the naira payment to the merchant. Then there must be dispute resolution session too, incase any of the parties tried to be shady. But please, the platform is first for us the company, where we can buy and sell ecurrencies and Cryptos to our customers. This feature of merchants is allowed, just Incase customers don't find what they need through us, and some merchants are offering it. It thus means that advert session of the website should be relatively tiny and at the bottom or side of the website. Also, when a customer wants to buy or sell to us or to any merchants, a chat box should be available for them to be able to chat with us or their merchant, if they are trading through a merchant. Ofcourse, when a customer has filled the trade order details, some important information cannot be edited, after submitting the order.