This video explains why border wall won't stop illegal immigrants into the U.S.

This video explains that building border wall will not decrease illegal immigrants into the United States from Mexico or from any other country, because not all illegal immigrants in the United States are Mexicans or migrate through land border from Mexico

 Many illegal immigrants in the United States didn't come by land border, many of them came into the United States by air with visa, and plenty of them over stay or fails to return to their respective countries after their visa had already expired and automatically becomes illegal immigrants migrated into the United States from different countries...

Building wall will cost United States billions and will also hurt Mexicans living at the border, because the wall is going to destroy their shelter and farms.
It is advisable for President Trump to increase border security, both land and airport and probably make some changes to their immigration system..