30 sec to 1 min exercises

https://imgur.com/a/mcspXph

I struggle a lot with seeing the whole picture and I often get stuck on one part of the drawing. Often times the legs are different size than the torso and the head is either way too big or too small. My biggest issue is drawing the head (hence why most of the sketches have an incomplete head or just no head at all). Would really appreciate some tips!