My grandmother wants to come to the united states to live from germany. what does she need to do to be here legally?

Your grandmother will need a U.S. Citizen immediate relative, as defined by U.S. Immigration law, to sponsor her. It is unclear whether your mother is a U.S. Citizen, but if she was, then your mother could sponsor your grandmother. In addition, she will have to be legally admissible to the U.S. Depending upon her age, there are a few grounds that 'may' bar her entry. Although this may seem remote, inadmissibility is possible. If you were a permanent resident, and chose to become a U.S. Citizen, then you could sponsor your mother, who could eventually petition your grandmother. However, this is speculative in that it is possible that by the time all of these events took place, she may have changed her mind. She may want to see how it is to visit the U.S. and spend some time with you, should you have lawful status in the U.S. As a German Citizen, she is allowed to visit for up to 90 days. She cannot have immigrant intent for the purposes of the visit, but she can get an idea as to whether this is more than a fleeting idea. At times, there may be other means to immigrate. Some have vast sums of money to invest. Others, may be single and looking for companionship. A few may have skills that are needed in the U.S. in spite of their age. If she has interest, she should speak with an experienced immigration attorney to find out what resources or reasons are fueling her desire to live in the U.S. It does make a difference to know what is actually available and possible, rather than what people say is possible, only to spend time preparing, documenting and spending significantly more money on the USCIS filing fees without results.