chmod

# Linux permissions
# User Group and Others
0	No Permission	---
1	Execute	--x
2	Write	-w-
3	Execute + Write	-wx
4	Read	r--
5	Read + Execute	r-x
6	Read +Write	rw-
7	Read + Write +Execute	rwx

# no need to memorize all of this; instead learn the following
0	No Permission
1	Execute
2	Write
4	Read

# To recursively remove execute permissions from files without touching folders
If you are fine with setting the execute permissions for everyone on all folders:

chmod -R -x+X *
The -x removes execute permissions for all
The +X will add execute permissions for all, but only for directories.

# fix cannot ls permission issue
chmod 775 .

# give read write execute permission to other users in the same group as the owner(user)
sudo chmod 770 -R username