If you decide to form a company outside of Germany, do not make your decision based upon ill-advised notions of tax haven jurisdictions. Tax haven jurisdictions can be beneficial for trusts or investors that have passive income (money from stock dividends or bond interest) but generally are counter-productive for a small business that actually sells a product.

A natural progression for a new online adult business is to go from free sites and traffic generation to a pay site or other model that has billing needs. If you want to begin billing, you will want a company either in the Visa EU region or Visa US region. There are burdens and benefits to both Visa regions, but you will need a company presence in one of those regions to use those billing solutions, so a company on some Caribbean tax shelter island will be of no use.

You need to examine your business plan, tax issues (do not neglect VAT issues!) and regulatory compliance. Do not believe someone that tells you server location dictates jurisdiction! Where your company is formed and where your customers access your service is much more important than the location of your primary servers.