Installing Drupal

I have a near-stock 4.7 install, with the Porter-Stemmer module added on. Pretty much everything works fine, except, entering a search phrase results in the following errors:

I have a CMS working fine on my webhost, but would like to give Drupal a try. Can I make a subdirectory on the site and set drupal to take a new domain name keeping the original domain working as before?

Regards,

Hallo!
I just find Drupal! And I have no idea how to install because I m not a developer!
Someone will assist me to full installation process? Thanks

I have path auto module, that makes from /users/34 the short url user/his_name.
the thing I faced today that users used numers (!!) like 111 in his name. e.g. it
were created "/user/11111" alias for "uses/100" (real situation, happy 100 users of my site made mess and was blocked ;-)

question: what will be when user number 11111 will be register, but the alias for him will be occupuied?
what is the best solution to prevent it?

This is the first time I am trying out this CMS, so it's new to me.

I am running lampp (or xampp, same difference), so the server is running fine.

I followed the installation instructions to the T, and when I fire up drupal (which I have tried just installing into a directory called drupal, and retried just in my root htdocs directory), it is just a plain white page with some css stuff code at the top, and it told me to create an account, etc...

After just trying to install the taxonomy_access module, replacing the default taxonomy.module with the patched version because the patch wouldn't apply properly, and running the SQL script there is one slight problem - With the module enabled in the "modules" administration dialog the configuration page under settings>taxonomy_access looks like: