I am interested in the group algebras of non-locally compact groups. What references can you advise?

This is a wide question, so I list more concretely what I would like to see:

Here X can be even any Tychonoff space. Is there a description of the dual space of C0(X) as measures, or some close theorem? I have found a theorem in [H. König, Measure and integration] which describes measures as the dual of some space of semicontinuous functions. It is interesting, but I want the opposite: let the functions be "good", what measures will we get?

Are there any algebras, which consist more or less of measures, and can be associated to every topological group, or at lest to a Polish group? I've seen treatments of (left) uniformly continuous functions on groups and their dual space which is a Banach algebra. Is there a good survey of the topic? Are there other algebras?

Thank you, and obviously I would greet more than one answer.

**EDIT:** Question 1 is answered below, and for question 2 I have found meanwhile a paper and a bunch of references in it: Anthony To-Ming Lau, J. Ludwig: Fourier–Stieltjes algebra of a topological group, Advances in Mathematics 229, Issue 3 (2012), 2000–2023. For my purposes, this is enogh at the moment, so I close the question.