Congrats on the new horse.
I liken horse buying to marriage after a speed date. Almost no-one is willing to trial horses any more, so you get 1-3 rides and a PPE, after which you need to make a decision. It can always go poorly. But you sound like you’ve had good guidance and you’re taking your chances with what seems like a good one.
I bought a mare 4 years ago after just 2 rides. She’s everything I could have hoped, but we’ve had our ups and downs. She’ll be Third level dressage this year and I love her to bits. The horse before her, I rode once, and based on my trainer’s encouragement, I bought him and brought him home. He took me from First Level to PSG and was the most wonderful unicorn you can imagine.
Have fun and enjoy the ride!