People are gossiping, backbiting and looking down on me. Must I fight for my right or leave it to Allah. Must I go to any functions where these people (including relatives) are? One of them even scolded me in a mosque. Please help.

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.

The Holy Qur'an and Sunnah give emphasis to "the quality of pardon." Allah says: {…but whoever forgives and makes reconciliation, his reward is due from Allâh. Verily, He likes not the Zâlimûn (oppressors, polytheists, and wrong-doers, etc.).} [42:40]
Imam al-Tabari , while commenting on the above verse says: 'whoever pardons an offender and does not revenge an insult although he is able to do so, just for the sake of Allah, Allah will reward him.'
Allah says: {Repel evil with that which is better. We are Best-Acquainted with the things they utter.} [23:96]
In the same vein, the Prophet (Sallallahu Alaihi wa Sallam) said: "One who in spite of having capacity to avenge (a wrong) controls his anger, will be singled out and called by Allah, the Holy, the Exalted, over and above the multitude on the Day of Judgment, and given to choose a beautiful Houri with beautiful eyes." [ Abu Dawood and al-Tirmizi , narrated it as a good Hadith]
Another Hadith recorded by Muslim from Abu Hurairah (RAA) that a man said to Allah's Messenger (SAW): 'O Allah's messenger! My relatives are such that I co-operate with them, but they cut off; I am kind to them but they ill-treat me; I forbear and they are rude to me. The beloved Prophet (Sallallahu Alaihi wa Sallam) said: "If you are as you say, you are feeding them with hot ash; and so long as you continue as you are, Allah will help you and He will protect you against their mischief" .
Imam al-Nawawi (may Allah's mercy be upon him) said: 'this Hadith means that your good treatment with such people is like feeding them with hot ash due to their bad response. 'Feeding them with hot ash' shows us what bad harm will befall them due to boycotting and harming him (i.e. the good-doer). It also means that your good treatment with them constitutes a form of degradation and disgrace against them because you treat them kindly and they respond wickedly.
Therefore, it is better for you to avoid responding badly to their bad treatment. But, if you think that your good treatment and silence will increase their ill treatment, you can discipline them even with a sharp word.
Then, you can participate with such people in a gathering as long as there is nothing Haram. Also, being with them depends on your interest as a Muslim.
Allah knows best.