Hello welcome to the forums. Your camera can only focus on one thing at a time. Also what focus points are you using. With mirrorless cameras unlike DSLRs they track focus all the time. So all of your focus points are active even if your not using them. What focus mode are you using and exposure mode. Please post some pictures to show the forum what's going on.
EF 16-35mm F/2.8L III USM, EF 24-70mm F/2.8L II USM, EF 28-135mm F/3.5-5.6 IS USM, EF 50 F/1.8 STM & EF 70-200mm F/2.8L IS III USM
EOS 40D & 5D Mark IV
430EX III-RT & 600EX II-RT
i am using manul explosure %90 of my settings Shutter 1/125 Apt 6.3 iso 200
as you can see firs photo perfect focus with face but rest of body ummmmm so so
First photo shoot with US$ 1700 Canon EOS R
as you can see in the second photo entire body focused perfecty
shoot with US$ 600 Canon T7i
These two shots aren't really a good comparison example. The model in shot two (T7i) is more compressed than shot one. Her knees are near chest level which makes her feet quite a bit higher. Shot two has no EXIF data, so I assume you are using the EF-S 17-85mm f/4-5.6 IS USM for both shots as the EXIF info states in shot one? If so, this could make a difference, using a crop EF-S lens on the full frame R. I have some EF-S lenses that I use on my R5 and they behave differently than my RF glass, plus the massive MP hit.
Another thing you could try is stepping back and increasing your FL and keep your current aperture. That would give you better DOF. Stopping down to f/8 (as mentioned by others) would work depending on your lighting as you'll need more light.
BTW, nice shots!
What lens were you using? Based upon the focal length, distance to your subject and the aperture, that will establish what the depth of field will be. As we typically focus upon the eyes, you'd need to ensure that there's enough depth of field behind the eye as well as a bit in front of it.
Of course this can vary if the person say has one of their shoulders facing the camera; more depth of field would be needed.
Also, are you using a tripod? If you are say tilting the camera a bit such that the person is now no longer parallel to the camera's sensor, some parts of the body may then be outside the depth of field.