Normaly we would say James's car but is it also acceptable to say for instance the car of James or it sounds just awkward and no one would say that?
1 Answer
Cambridge Dictionary gives some guides on the use of the 's and the of-phrase:
When we don’t use of
When we are talking about things that belong to us, relationships and characteristics of people, animals, countries, categories, groups or organisations made up of people, we usually use ’s:The men’s dressing room is on the left at the end of the corridor. Not: The dressing room of the men … The cat’s paw was badly cut. Not: The paw of the cat …
When we don’t use ’s
We don’t use ’s when the noun is not a person, animal, country, organisation, etc., or when the noun phrase is very long
OP's example belongs to the first category.
As an aside, there are different guides on whether to use 's or just the apostrophe for proper names ending with s. The same dictionary says
When a first or second name ends in -s, we can either add ’ or ’s. It is more common to use ’ than ’s.
Is that James’ car? (or Is that James’s car?)
We can use either one but should be consistent.