So you believe all truth is relative?
To me, if truth is relative then truth is not a relevant value between us.
And, I'm not saying this is wrong, only that in dealings between individuals, truth is not useful.
So "truth" has no actual value, even among friends.
No, not really.
Here are 3 versions of truth, here are the first 2 ones:
There is one version, that works on everything.
There is no truth at all and everything is relative.
Now these 2 are both too simple.
So here is a simple trick. Consider truth a human behaviour. Try it and here is what it leads to.
The 3rd version:
Truth is how humans understand(a human behavior) and explain(also a human behavior) something, which matters. But just as all other human behavior this is neither everything/absolute nor nothing/absolutely relative. Truth is about explain how the world works for humans as behavior and there is not one behavior for everything nor is a behavior nothing if it can't do everything.
In other words as it connects to the 2 overall claims of behavior:
Only that, which is shared through observation and build upon, matters. (Matters is an human evaluation, a behavior)
Only that, which makes sense and matters as the existential questions of being a human and how to deal with that, matters.
Here they are in another sense: Only what is external to the human mind matters or only that which is internal to human mind matters.
So back to truth: There are more than these 2, but there are the main ones: External and internal truth.
We can expand and differentiate a lot more, but if you look closer they are both here as what science can and can't do.
https://undsci.berkeley.edu/article/0_0_0/whatisscience_12
Now as knowledge. Knowledge about what we all share and how we deal with being individual.
The first one is science and the second one is social science, human science(yes, that is a form of science), religion and philosophy.
So how gravity works is one truth and how to be a human are many truths, yet you can learn to do it for the concept of humanity. Not that the last one is better than any other human truth, but it is possible.