Trade negotiations

"The British government has said it wants to keep the UK in the EU single market for goods based on a common rule book. In order to avoid customs checks, the government wants an unprecedented customs system where the UK would collect EU duties, while having the freedom to set different tariffs on goods destined for the British market."

(The Guardian.)

I'm trying to understand the Brexit negotiation between the EU and the UK and I've got to admit that more often than not I can't get exactly what's going on regarding the trade talks.

I understand the description of the "unprecedented customs system" like this:

To avoid a hard international border between Northern Ireland and Republic of Ireland and to keep the UK outside the EU's custom union at the same time, the UK is going to collect itself the EU's custom duties from the UK's exporters of goods which are to be delivered on the EU territory and return those duties back to the EU's taxmen "while having the freedom to set different tariffs on goods destined for the British market".

In other words, the UK, as a country, would control the duty operations (regarding the British export to the EU) not only on its side of the border but also operations meant to be done on the other side, i.e., on the Republic of Ireland's side, thus excluding Ireland's custom officers from the direct collecting of duties from the British exporters to the EU.

Is my understanding correct?