I’m not clear on whether you’re looking for one big query that returns all the ‘track_trip’ and ‘training’ posts, sorted by the two different custom meta fields, or two separate queries. But either way, you’ll need to use a custom meta_query. You will probably also need to orderby meta_value_datetime. Note in the “‘orderby’ with multiple ‘meta_key’s” section of the WP_Query documentation you can orderby an array of values, if that’s what you’re looking to do.
