If I have invented something, how can I get it patented and represent it at world level?

Hi,
Here is a brief answer to your question, which cannot be a full legal advise. For further information, a patent agent/attorney should be consulted.

As you have already found out, patent protection works on a national or regional level. A patent is a temporal monoply given to the inventor/applicant by the respective jurisdiction, i.e. single nations. Thus, protection will always be on a national level.

(International) patent applications in a nutshell:
you can apply for a patent at an international organization: WIPO (www.wipo.int). Such international patent application can later be "converted" into one or more national/reginoal applications. The grant of a patent will then be on a national/regional level though. Optionally, you start with a national application and within 12 month you can file another application claiming the priority of the first one. This second application can be any national, regional or even internation application. In the meantime you may have received search results for prior art regarding the first application, which helps you deciding to continue and where.
As I said, it is a complex system, so the above is only a brief overview.

Oliver