Befriending kuffaar

Four days ago a Hindu friend of mine was showing me the idol and addressing it as god and asking me like "do you know what this god's name is?" I in my heart I knew that Allah is the only lord and there is no god except Allah but I told him I don't know his name and then he told me it's name and then I said I have heard it in some movies. Was there any kufr in my statement because I did not tell him directly that the idol is not god and when he asked me "what is the name of this god?" I said I don't know. By seeing the scenario it looks like I don't know that god's name (but in my heart I knew Allah is the only god). I usually read the shahdah after every wudu. This happened on Thursday and I started getting doubts about these statements on Monday. So if that was kufr and I have prayed Salaah for four days, should I pray again but I read the shahadah Thursday itself after wudu. Were my salaah valid?