Praise be to Allah.
Yes, the matter is indeed strange as you said.
But what is strange is not merely the fact that a Christian man has married a Muslim woman, even though this marriage is definitively prohibited in Islam, according to scholarly consensus. That is not the only strange thing about this case, for the Shaytaan deceives many of the children of Adam, until he causes them to fall into something that is even more abhorrent than that.
What is even stranger is your concern to ask about such a thing, you and your wife, or – to be more precise – your concern to help your wife in such a matter, which is indicative of your great care for her and your desire that she be happy, when you do not care about the most serious aspect of the relationship between you.
What we mean is the basis of this invalid relationship between you, which is fundamentally wrong.
Therefore we will address you directly, as you are the one who has asked us and you are the one who is responsible for this grievous mistake, and tell you that it is not permissible for you or for this woman to continue in this relationship at all, not even for a single hour. Rather what you must do is separate, for she is not your wife and is not permissible for you, and you are not permissible for her so long as you remain a Christian.
Regardless of whether you spend Ramadan in the east or in the west, in Dubai, or in the city of the Prophet (blessings and peace of Allah be upon him), or in Berlin, none of that will change the matter in the slightest, and will not fix the basic flaw in the relationship between you.
Rather you must separate.
Then once you have separated, it is not permissible for you to go back to her unless you truly seek Islam because it is the final religion of Allah, that He loves for His slaves and wants from them.
Therefore we call upon you – as you are keen to make your wife happy and make things easy for her – to leave her immediately, because her staying with you means that she will lose out a great deal in religious terms, which would result in misery for her in this world and the hereafter, if Allah does not shower her with His forgiveness and mercy. Then you must spend some time reading about Islam and learning more about it. The Islamic centres in your country can help you with that.
If Allah opens your heart to Islam and you become Muslim, then in that case there would be no impediment to you marrying her with a new marriage contract, in accordance with the teachings of Islam, whenever you both want to do that.
Then you can begin your married life with sincere repentance that will erase the errors that came before it, for Allah, may He be exalted, forgives those who repent and turn back to Him, no matter what sins they committed before that.
We ask Allah, may He be exalted, to guide you to the truth.
And Allah knows best.