Can I get sued for using someone elses photo if the offered it to me?

You can always be sued, by anyone for anything, but that doesn't mean that you will lose the suit. If the owner of the photo gives you the right to use the photo, and that person has the capacity to consent (I add this because you are 16; if the person who sent you the photos is also a minor, he;she may not have the legal capacity to consent), and you only use the photo in the manner to which the owner agreed (for example, if the owner gives you the right to use the photo in some artwork you are creating, that doesn't mean you have the right to use it in an advertisement, or if you induce them to send you the photos by telling them you are going to use the photos in a video tribute and then make a negative video instead), you have the right to use it.  You  have to be careful that the person giving you permission owns the legal rights to the photo in the first place.  In some scenarios, the person who sent you the photo may not have those rights.  For example, he/she may not be the photographer, or may have given the rights to use the photo exclusively to someone else, etc.