Strange syntax error in if condition - Shell Script - bash

Question

So I'm making a shell script in Ubuntu. It's purpose is simple. You give a command with arguments and you get a different operation each time. The problem is that when I run the the script it won't actually run because of a syntax error in one elif. The most suspicious thing is that I have a similar elif above wich works or at least doesn't pop a syntax error...
I'm leaving my code for you to see it and understand. Thanks in advance!
if [ "$1" = "-a" -a $# -lt 3 ]
then
echo "Add a new line in katalogos!"
read -p "Give me a name... " name
read -p "Give me a surname... " surname
read -p "Give me a city name... " cityName
read -p "Give me a phone number... " num
echo "$name $surname $cityName $num" > katalogos
elif [ "$1" = "-l" -a $# -lt 3 ]
then
echo "Content of katalogos will be sorted numerically and blank lines will be excluded!"
sort -b -n katalogos
elif [ "$1" = "-s" -a $# -lt 4 ]
if [[ $2 != *[!0-9]* ]]
then
echo "Content of katalogos will be sorted according to the second argument!"
sort +$3 katalogos
fi
elif [ "$1" = "-c" -a $# -lt 4 ] // syntax error
if [[ $2 = *[!0-9]* ]]
then
echo "Content of katalogos will be sorted according to the keyword!"
if [ $(grep -e "$2" katalogos | wc -l) -eq 0 ]
then
echo "String is not matched."
else
grep -e "$2" katalogos
fi
fi
elif [ "$1" = "-d" -a ( "$3" = "-b" -o "$3" = "-r" ) ]
if [[ $2 = *[!0-9]* ]]
then
echo "Katalogos's string matching lines will be deleted and blank lines will be in their place, assuming that the third argument equals -b, else just the lines will be deleted!"
if [ $(grep -e $2 katalogos | wc -l) -eq 0 ]
then
echo "String is not matched."
else
if [ "$3" = "-b" ]
then
sed -i "$3" katalogos | sed -i '$ a '
echo "A blank line inserted in place of the deleted one."
else
sed -i "$3" katalogos
echo "Line deleted."
fi
fi
fi
elif [ "$1" = "-n" ]
echo "katalogos's number of blank lines will be shown with the ability to delete them!"
grep -cvP '\S' katalogos
read -p "Do you want to delete them? Type 1 for yes or 0 for no... " ans
if [ $ans -eq 1 ]
then
grep -cvP '\S' file | sed -i
echo "Lines deleted."
fi
else
echo "Help centre!"
echo "-Type ./telcat -a to insert a new line to katalogos."
echo "-Type ./telcat -l to see the contents of katalogos sorted numerically (excluding blank lines)."
echo "-Type ./telcat -s plus a number to see the contents of katalogos sorted by the data that the number points to."
echo "-Type ./telcat -c plus a keyword to see only the lines that match with the word given."
echo "-Type ./telcat -d plus a keyword and -b or -r to delete the lines that contain the word given. Specifically if the third argument is -b it will automatically add a blank line to the deleted one and if it is -r it will not."
echo "-Type ./telcat -n to see the number of blank lines of katalogos."
echo "End of help centre!"
fi