How to use meta query

I struggle with a template for a custom post type showing some associated data.

I have set up three custom post types:

  • Trainer
  • Halle
  • Training

Each training has training times. For each training time a trainer and a “halle” is associated.
The trainer for the training can differ depending on the timeslot.
In order to set up the relationship I used ACF repeater fields with the following data:

  • Day of the week
  • Time
  • Trainer (relationship to CPT → Trainer)
  • Halle (relationship to CPT → Halle)

For displaying the data on a the training post type this works out.

But I currently struggle how I shoul configer the site of a trainer (template for this post type).
There I want to display all the trainings that are associated with the trainer.
I thought this is possible, but somehow I did not find the way to achieve this.

I set it up like this:
Loop
Type → Post
Post Type → Training
Meta Query:
meta_key: trainer
meta_value {post_title} (should be associated with the trainer of the current page.

What am I doing wrong?