Please tell me if I committed shirk/kufr. I saw a video of a girl talking about a serious topic online and she was wearing a cross. Does watching videos of people who wear a cross take me out of islam? (The video didn’t have anything to do with christianity though) Or if I have a non-muslim friend who wears a cross and I take pictures with them, does that mean I committed shirk/kufr? This happens a lot and I get worried every time but I’m not sure if I actually have to repent or not so that’s why it keeps happening.
According to the Holy Qur'an, Kufr means covering and concealing something, to disagree, to reject or not to give declaration to any one of the commands and prohibitions bestowed by Allah (SWT) and shown by Muhammad (PBUH).
On the other hand, shirk in Islam is used to refer to polytheism, which means worship of deity-gods (this ia major shirk),or ascribing a partner or rival (peer or counterpart) to Allaah (The Exalted) in Lordship, worship or in His names and attributes.
Allah (The Exalted) says in the glorious Quran :-
“Then do not set up rivals unto Allaah (in worship) while you know (that He Alone has the right to be worshipped)”
"Let there be no compulsion in religion. Truth has been made clear from error. Whoever rejects false worship and believes in Allah has grasped the most trustworthy handhold that never breaks. And Allah hears and knows all things." Al-Qur'an 2:256
Our Beloved Messenger (Allah bless him and give him peace) said:
Verily the religion is ease, and no one shall make the religion hard except that it will destroy him. So be balanced, do your best, and rejoice! And seek help in the morning, the early evening, and something of the night.”[Sahih Bukhari]
So,First of all, you have to have the basic knowledge of Islamic shari'. Just watching,listening something wrong, bad thoughts alone do not render a person out of the folds of Islam. Many times people get bad thoughts of kufr/shirk, that is not actually sinful. So definitely what you've experienced isn’t a shirk or kufr, unless you believe in it(what you've seen on the video or elsewhere) or rejects something that Allaah has commanded us to believe in, whether you reject it in heart without uttering it, or speak it, or you do an action which is putting one beyond the pale of faith.
Again, taking pictures with non-muslim friends or strangers can't take you out of the folds of islam. However, if your non-muslim friends discourage or refrain you from following islam or have bad effects on your beliefs, then you should try to manage the friendship so that you stay away from its bad effect. May Allah (the all Knower, the High, the Might) help you.