How we cannot see prohibited things (girls) especially if we are in the country of evil (Tunisia)?

Praise be to Allah, the Lord of the World; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

Imam al-Tabrani narrated in his book 'al-Mu'jam al-Awsat' from Abu Darda that the Prophet (Sallallahu Alaihi wa Sallam) said: "No doubt that knowledge is acquired through learning and patience is achieved by being patient, the one who seeks good is granted that, and the one who avoids evil is protected from it" . [Sheikh al-Albani graded it Hasan in his books Sahih al-Jame and al-Silsila al-Sahiha].
The above Hadith proves that Allah will surely grant good to the one who continues to strive to acquire it. The one who makes every effort to save himself from evil surely Allah will keep him safe from it.
Therefore, our questioner brother should know that 'Taqwa' (God-fearing) and strong faith could only be achieved by seriousness and hard work. Avoiding sins and evil is only possible by adopting the ways and means that help one avoid them. Abiding by the following instructions may be a great support to avoid forbidden things that are presented on TV, Internet, etc.
1) Befriending pious persons who help in doing good and encourage goodness and avoiding bad company.
2) Continuing to remember Allah as much as possible in addition to reciting Qur'an continuously.
3) Reminding oneself of Allah's punishment for sins and transgression of His limits.
4) One should know that the torment may come to one because of his sins in this life since it is proved from the Prophet (Sallallahu Alaihi wa Sallam) that sins block the sustenance.
5) One should bear in mind the bad end of his life, i.e. should fear the bad and of his life.
6) One should avoid using any material that contains forbidden pictures even if he is alone by himself since Satan is with the solitary person and he is far from two persons.
Allah knows best.