You can Use existing crypto payment processors.  Thats the s easiest and most recommended method for most businesses. the payment processor will help handle the complex technical aspects wallet management, blockchain monitoring, fiat conversion, compliance for you. You have options to typically integrate them via plugins for e commerce platforms or their APIs for custom sites just like yours.... The sites usually walks its client through the whole process so you don't have to worry much but choose a reputable one at that..

here's a list of few BTC payments process on GitHub..
But if you which to also go for altcoins then you can try out bitpay or CoinPayments those are the few reputable ones I can recommend for now...