Why is there an extra space when I type "ls" in the Desktop directory?

The extra space appears when you have file names in your directory needing ' around them (e.g. file names with spaces or other special characters).

~/mytmp$ ls
 a           'file(abc)'         proyecto3.csv   test         Test.sh
 b           'file(ab,c?).mp4'   rootfile        Test1.txt    Test.zip
 F26         'file(abc?).mp4'    scr             Test2.test   vowels
 Feb          guess              script          Test2.txt
'Feb 26 xx'   hw                 something       test.rar

After removing the 'strange' files I get:

~/mytmp$ ls
a    guess  proyecto3.csv  script     test        Test2.txt   Test.sh
b    hw     rootfile       something  Test1.txt   test.rar    Test.zip
F26  loop   scr            speak      Test2.test  testscript  vowels

I'm pretty sure file1 file2 file3 is not what's exactly shown on your screen. You omitted precious information (the actual filenames) that might easily be relevant.

My assumption is that you have a filename that contains a space or other special character.

Newer version of coreutils's ls quote such filenames, typically in single quotes. Plus, if there's at least one file requiring such quoting, it adds a space in front of all other filenames so that they align up "nicely" if they happen to be underneath each other, that is, the single quote mark (apostrophe) is ignored for alignment.

See --quoting-style and -N in the manual page of ls for some more details, and the section "Formatting the file names" in its info page for even more details. You might e.g. consider aliasing ls to ls -N.