How can I determine if I infringe a patent?

I agree. Speak with a patent practitioner. There are search services that do "freedom-to-operate" checks, but they need to be interpreted by someone who understands patent law and the tech landscape (along with having the confidentiality of an attorney). Remember, if the patent owner can prove you were aware of her patent and infringed that patent still, you may be liable for treble damages.

You will definitely need a patent professional to help you, and you will need one who is extremely experienced in your particular niche, meaning, cloud files, social media, software and other platforms. Basically, however, to infringe one or more claims of a patent, your invention/system, whatever you have or are implementing, must include every component of the patent claim. If the patent claim recites something that is not in your invention/system, you do not infringe - which is precisely why you need an experienced patent practitioner to truly appreciate what the various components of the systems are, how they actually function, and what their equivalents might be.