So basically i want to make a User on my laptop for my little bro and I was wondering if there was a way to only give him access to specific applications or to lock my applications behind a password?? and id also like it so he cant install programs etc
First of all, welcome to Manjaro 
To install programs you mostly need root password.
Except the first user which can use it’s own password, this is a special account.
(Has to do with group ownership etc)
If you’re worried about your personal files, don’t worry because every user has it’s own homedir with own personal files.
No idea how you would be able to restrict usage of system-wide installed applications though, because they are meant to be accessible by all users of the system.
There might be a way to customize his account where you remove certain applications from his menu, but i have no idea at moment how to help with that.
Unless you impose some serious customized user:group segregation you can’t restrict a user from running the applications installed on the system.
Even then I think the segregation will be to complicated to maintain in long run.
thanks for the answer 
thank u so much
I would just keep moving the binaries in /usr/share/bin to smewhere else like /usr/protectedbin, then you would modify $PATH for yourself and for root so you and root stil could run those programs.
Many issues you would neet to automate later, like making sure the binaries are not reinstalled after package updates.