Can someone help me with clustering DGE datasets?

Suppose we have users, for each user, we have: user_id, user_name, user_job title, user_skills, user_workExperience. I need to cluster the user based on their skill and work experience( long text data), put the users into groups. I was searching about how to clustering text data but still didn't find a good example to follow" step by step". Based on the data I have I think I should use unsupervised approach (as the data I have is not labeled), I found that I can use K-Mean or hierarchical clustering, but I'm stuck in how to find: K "number of clustering with K-Mean". Also, I don't know what is the best way to prepare the long text before fit into the clustering algorithm.