I dont have any pyrs, but I believe female dogs all around the world are pretty similar, just like us
Smaller dogs usually have a first heat when they are around 6 months or so. Then it seem like the bigger the breed the later the heat. Around a year is probably a good average. Mind you it can be a bit earlier and also a lot later. My Hera came into heat first time when she was a little over 14 months.
As good as all of them swell in the rear end, gets floppy and the dishcharges start, it is usually clear, but kinda slimy, so if you dont look for it, it can be easy to miss. From that day, when the dishc. starts it takes around 8-10 days before a female would stand for a male, when she does she is in the prime of her heatcycle. And thats when the little fourlegged babies are made
Once the dishc. goes over to be red and bloody, you will most likely have to put on a diaper, or pantie as we call them here
Most large breed dogs bleed quite a bit and especially when they have been sitting or laying down and stand up, it can be a bit like "oops who turned the tap on" Some gets a bit grouchy, other youd never be able to tell by their mood.
After the heat is over, they can actually have problems with hormones, they think and feel it like they are pregnant, they get all the signs as if they were and start to nest and can even fill up with milk, can gather all their soft toys and put them in their bed and "nurse" them. I had a dane once who we showed but wasnt really up to standard to breed and she had so bad problems after a heat so we decided to retire her and spay. But most dogs do fine.
One more thing, about 8 - 10 weeks after the heat (about the time they have puppies if they are bred) they can get uterus inf. you'll notice she drinks a lot more, and seems kinda off, and pees way more, just little signals to start with. If you want to show her, I would absolutely do that, let it go a couple of heat cycles and see, most likely she will handle it just fine, most dogs do.
I am sorry this got to be a novel, I just seem to get all carried away over blood and goe, and dishcharges