On the surface it appears to be a website development platform, based on templates which allows a novice user to quickly build a professional looking website with still image and video content as well as relevant textual content to market their products or services. There are literally many thousands of sites like this, all designed with the same purpose in mind, a buffet or cafeteria style selection of generic formats with customization capability so that someone can quickly and easily gain a web presence without considerable cost and time associated with hiring a true web developer.
The site is hosted in Germany and it's native language is German.
That said, I don't see a place to enter a code as you mention however there is an account creation portal where someone would make a unique user ID and password to have private access to their site building process.
Just because this appears to be legitimate doesn't mean there can't be ulterior motives to his request of you and that there isn't one or more underlying layers of web pages with other purposes aside from the obvious.
Best advice is to steer clear of anyone who you don't know well (especially someone you're just starting out in a relationship with), and who asks you to "enter a code" into a website. Furthermore be absolutely sure that you do not provide ANY personal information beyond what you already have, as this could be used by someone for illicit or unethical purposes without your knowledge.
Most importantly do NOT provide your most sensitive personal information such as Social Security number, Date of Birth, credit card numbers, information regarding family such as mother's maiden name or anything else that would be crucial in uniquely identifying you. Identity theft is huge and those that commit it are often masters of deceit, portraying themselves as your closest allies only to be your greatest enemies and be operating for personal gain.
To them you are just a number, another means to an end result which is to secure your personal information and steal money or worse, your entire identity. They feel no guilt and have no remorse fit the terrible hell they put their victims through. Please be careful.
Sent from my XT1585 using Tapatalk