Where can I find branded tires for my BMW 1 Series 118d Catalytic Converter online?

Where can i find the dealer of car spare parts online. How can i find the Catalytic converter is genius or not?

Start with new parts at places like RockAuto.com, AutoZone.com, and many others.
You’ll need all the, so far, missing information about your car.
And, so far, your post is confusing . . do you want tires ? do you want a catalytic converter ?

Is there any such thing as a “unbranded tire”? Every tire I ever saw had a brand.

“Catalytic converter is genius” ? what does this mean?

I am not going to flag this OP or call them a Troll but when you look at their other posts it makes you wonder if they just playing around.

@emmaolivia does not live in the USA. The 118 model is not available here. Do you want tires just like the original equipment tires? You may also mean genuine catalytic converter and not genius. You can be sure the catalytic converter is genuine if you buy genuine BMW parts. There should be markings on the converter and its packaging that tell you so.

I was unable to find out on the internet…
is the “d” a diesel?

BMW 118D is 4 cylinder diesel , not sold in the USA.

We’re probably not even familiar with its emissions system over here.
However, I’m sure your home country must have a source on the internet for the parts needed.
Sincere best.