The pray in Friday noon in Sierra Leone is in the Sierra Leone language and I didn't understand any word for that. Can I pray in my room?

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

Muslim jurists are of different opinions concerning the matter of delivering Friday sermon in other than Arabic language whether this is allowed or not?  The majority of Muslim scholars are of the opinion that it is permissible at the time of inability.  This was decided by the Islamic Fiqh Council.  The text of the resolution is as follows:

"The most just opinion that we adopt is that delivering Friday or Feasts sermon in Arabic language in non-Arabic countries is not a compulsory condition for the validity of the sermon.  However, it is better to say the forepart of the sermon and the verses from Qur'an in Arabic language in order to habituate non-Arabs to Qur'an and the Arabic language as well.  Because, this practice helps them learn Arabic and recite Qur'an in the language in which it is revealed.  Thus, an orator may explain, and teach the audience during His sermon in the language they understand well".

As for the second point, one has to attend Friday sermon whether he understands it or not.  If one asks what the benefit of attending is if one does not understand the language in which the sermon is delivered, the answer is that he does not lose at any cost, but at least he will listen to a verse from Qur'an or a Hadith which are generally mentioned in such sermons.

Moreover, you will get the reward of attending and listening to Friday sermon as reported in Musnad Ahmad and al-Tirmizi from Aws al-Thaqafi that the Prophet (Sallallahu Alaihi wa Sallam) said: "If anyone washes and bathes on Friday, then goes out early, sits near the Imam and listens without interrupting, he will have the reward of one year’s fasting and praying for every step he takes". 

Allah knows best.