I'm exercising with a home pilates machine called Burit. I've been doing this consistently for 3 months. I've been doing this consistently and it's been effective in just one month. This really targets the trapezius muscles. Since this originally came out as a home pilates machine, there are online zoom classes and many videos on YouTube.
It's difficult at first, but as you keep doing it, you'll feel your posture getting better. For your information, I've never had a personal trainer and I'm a total beginner at exercising.