If we visit any Muslim and he offers some food to eat, but we don’t know that the food is halal or not. Can we avoid eating if we have a doubt of halal and haram.

The ruling will depend on the extent of the doubt. If one is almost certain
that a certain Muslim does not know the correct concept of Halaal and is not
sensitive to Halaal and Haraam, then that is a sound reason to abstain from
eating such foods offered by him which is doubtful, for example, meat, etc.

In such a situation, one should apply his discretion and adopt wisdom and
diplomacy in his approach, probably, by eating only the non-meat dish. The
friendship may also be used as an opportunity to advise the person of Shari'
ah, Halaal and Haraam.

and Allah Ta'ala Knows Best

Mufti Ebrahim Desai