According to the latest news from well-known transfer expert Romano, Manchester United have not started active negotiations with Guimaraes, and meeting with the agent is just an industry norm.
Manchester United admire Bruno Guimaraes, but have not yet started active negotiations with him, nor have they submitted any contract renewal proposals to his agent.
Manchester United met with his agent a few weeks ago, but this does not mean that the two sides are negotiating a contract. The agent represents many players, and it is normal practice in the industry for top clubs to have regular meetings with top agents.