Question: The more i study science and maths these days, the more i continuously question myself whether all the knowledge we have built up until now is in fact true or correct. 

But before being picky with what true is, like i know in science that knowledge will never be perfected, as scientific theories are just theories which claim to understand the natural phenomena in a better way than before, justified by experimental verification. But the scientific theory or knowledge built may always be superseded with a better scientific theory, which questions whether at any point in time what we know from science is really true at all? 

This is just one aspect of the confusion which i am having; however, more generally, if i were to say everything we know up til now is wrong, does this claim have any validity? 

In other words, if i were to say that everything we know is wrong, is this considered true?

Answer: 
This is a very common issue when dealing with science. Much of science's approaches to Truth (with a capital letter) is through [abduction](https://plato.stanford.edu/entries/abduction/), an approach which assumes the most likely hypothesis is true. If you read the linked SEP article, this is fraught with nuances, as you suggest.

Personally, I am a fan of radical skepticism, and the [Aggripan Trilemma](https://en.wikipedia.org/wiki/M%C3%BCnchhausen_trilemma). It's not popular these days to declare that one cannot truly know anything, but if nothing else it's an interesting foil to challenge the current tendency for other systems of thought to declare they have the Truth.

As an example, I find it is *very* common to assume that we know the true semantic meaning of a word or sentence. While we tend to permit axioms to be challenged, tested, and sometimes proven, the behavior of the language we are using is typically assumed to be true (for good reason: there's major issues that arise with a language defining its own semantics). What if the answer is simply that we are not using the same meaning of "knowledge?" I might be communicating about what I believe knowledge is, and you might be communicating about what you believe knowledge is!

An interesting follow on might be to question how one might live life if nothing can be known, using whatever concept of knowledge suits you. I believe there are some related things targetted by Zen Koans, which many state are designed to try to break you out of the way you think. Do we really need to know Truth? Myself, I find the answer I get about that question depends greatly on the individual doing the answering.
It's impossible for everything we know to be wrong.

There is certainty in our thought.

Consider the following: (i) not everything is what it seems. This means that the objects of our thinking can differ from what we think they are.
This claim cannot be disputed without assuming its validity first. Thus, trying to dispute this claim necessarily leads to a contradiction. 

By the Principle of Non-Contradiction demonstrated by Aristotle in his Metaphysics, we know contradictions are not true.

From (i) [the possibility of error] it follows that the external world is not created by our mind, but rather, is independent of it given the possibility of inadequacy between our thoughts and the external world. 

Thus, we know something besides our conscience exists. 

This is an example of something you could know for sure, but by studying logic and a priori claims there is more you can discover.

A priori knowledge is the only we can have certainty about. Logic is a priori and every empirical scientist assumes the validity of logic in order to do science. Thus, any science has an a priori foundation. This foundation is what we can know for sure, the rest could be the case or not. But don't discard empirical knowledge for a priori reasoning is limited.