The Muslim must strive to find good friends who will help him to do good, as the Prophet (peace and blessings of Allaah be upon him) said: “The likeness of a righteous companion and an evil companion is that of one who carries musk and one who works a bellows. With the one who carries musk, either he will give you some or you will buy from him or you will notice a pleasant fragrance from him. With the one who work a bellows, either he will burn your clothes or you will notice a foul odour from him.”
Narrated by al-Bukhaari, 5534; Muslim, 2628, from Abu Moosa al-Ash’ari, may Allaah be pleased with him).
It is not permissible for a Muslim to make (close) friends with Christians or other kaafirs. Allaah says (interpretation of the meaning):
“O you who believe! Take not the Jews and the Christians as Awliyaa’ (friends, protectors, helpers), they are but Awliyaa’ of each other. And if any amongst you takes them (as Awliyaa’), then surely, he is one of them. Verily, Allaah guides not those people who are the Zaalimoon (polytheists and wrongdoers and unjust)”
“O you who believe! Take not as (your) Bitaanah (advisors, consultants, protectors, helpers, friends) those outside your religion (pagans, Jews, Christians, and hypocrites) since they will not fail to do their best to corrupt you. They desire to harm you severely. Hatred has already appeared from their mouths, but what their breasts conceal is far worse. Indeed We have made plain to you the Ayaat (proofs, evidences, verses) if you understand”
[Aal ‘Imraan 3:118]
al-Sa’di (may Allaah have mercy on him) said:
This is a warning from Allaah to His slaves not to make (close) friends with the kuffaar and take them as close confidantes or best friends.
Tafseer al-Sa’di, p. 198
The Prophet (peace and blessings of Allaah be upon him) said: “You should not make friends with anyone but a believer and no one should eat your food but one who is pious.”
Narrated by Abu Dawood, 4832; classed as hasan by al-Albaani in Saheeh Abi Dawood, 4045
And the Prophet (peace and blessings of Allaah be upon him) said: “A man will follow the religion of his close friend, so let each of you look to who he takes a close friend.”
Narrated by al-Tirmidhi, 2378; classed as hasan by al-Albaani in Saheeh al-Tirmidhi, 1937
So stop keeping company with Christians and replace them with Muslim friends, and try to make friends with righteous people.
You should note that it is not permissible for a man to keep company with females or with homosexuals, whether they are Muslims or Christians, because of the fitnah (temptation) involved in that, and because it also involves things that are forbidden in sharee’ah, such as being alone with them, shaking hands with them and things that are more serious than that. I ask Allaah to protect us all from fitnah.