Can Multisite solve my issue?

Yes, it’s possible, but it’s overkill. You could use categories on a single site instead. https://www.wpbeginner.com/glossary/category/

thank you for your reply, but i cannot understand how categories could solve my issue ??

Instead of making new sites for each vehicle type, you could have categories for them, then have pages listing only from the categories.

thanks again, but this is not possible, since there is a plugin that deals the cars, the options for the cars a dealed from the theme options,and many pages have created via page templates.

Ah, I didn’t realize you were using a plugin. You’d have to work with their devs on that.

unfortunately the developer in not offering any custom work, only support
https://themeforest.net/item/car-dealer-automotive-wordpress-theme-responsive/8574708

At this point, we’ve reached the limits of what most in the community here are willing to offer in their spare time (everyone here is a volunteer). You should consider hiring someone so that you can give them direct access to the site for a far more efficient fix than we can provide here.

From my point of view you got 2 choices:

• Hire a professional to customize your theme,
• begin to search for a theme/template that actually suits your needs.

ok, i would like to ask, if i create different installations for each vehicle category how can i connect them in order to appear one?
is there any plugin?

Multisite seems very good solution but all sites are on the same database, which i think is not very good.

Why would you think all sites in one DB is bad? I’m hosting 35K sites in one DB, and it works fine.

i was thinking keeping separate datebases of each vehicle category could be better to manage.

WordPress does all the DB management that you would need. No need to break it up into multiple DBs.