To get back to the original chicken/egg, position/time question, the answer is neither is first.
The key to this is that you get a set of Simultaneous Equations than when solved result in the three spacial coordinates + time being determined.
Time is not separate, it's just one of FOUR coordinates.
To get values for 4 coordinates you need at least 4 equations.
To get values for 3 coordinates you need at least 3 equations.
More satellites results in more equations.
Once turned into equations the maths doesn't care what the symbols represent, just that there is some numeric relationship between them.
I suspect that if you don't understand simultaneous equations (school maths at age less than 16 as I recall) you are not going to be able to 'get' this without a bit of study. If you can do basic algebra then extending to Simultaneous Equations should not be too big a step, otherwise maybe a bit more work. Bound to be some very good material on internet. Youtube? There is very likely a 5 min video somewhere that will make it all clear.
Now while I understand the concept of simultaneous equations, the spherical geometry (+ other stuff) equations involved in this are for sure completely beyond me:-)
PS One of the big on-line-universities was started by a maths teacher for his offspring. udemy, coursera??? Bet he has some good stuff that may have escaped the paywall (legitimately
.