What is the official website for bitcoin?

Bitcoin isn't a lawful entity but a collection of interoperable stuff.

Bitcoin.org is registered by the creator of Bitcoin and currently managed by those who maintain Bitcoin Core, the node implementation that is considered to be the "reference" one. Hence I suggest using Bitcoin.org

Bitcoin.com is owned by Roger Ver, who is interested in promoting Bitcoin Cash as Bitcoin. The website is supported by Bitcoin Cash fans and hated by Bitcoin users. (Citation needed?) You just need to be careful, what they have on their website Bitcoin Cash will not be applicable to Bitcoin. It might happen that "your transaction can't be found" because you're on their Bitcoin Cash explorer. When you're sure that you chose the correct coin, there is no downsides of using it.

What is the official website for bitcoin?

Bitcoin isn't a lawful entity but a collection of interoperable stuff.

Bitcoin.org is registered by the creator of Bitcoin and currently managed by Cobra, who is a controversial person but doesnt seek profit from it

Bitcoin.com is owned by Roger Ver, who is interested in promoting Bitcoin Cash as Bitcoin. The website is supported by Bitcoin Cash fans and hated by Bitcoin users. (Citation needed?) You just need to be careful, what they have on their website Bitcoin Cash will not be applicable to Bitcoin. It might happen that "your transaction can't be found" because you're on their Bitcoin Cash explorer. When you're sure that you chose the correct coin, there is no downsides of using it.