I need help connecting KPN cables

the black one is a "koppelstuk" 

you can find it via this link: 

https://www.bol.com/nl/nl/p/utp-ftp-cat6-rj45-koppelstuk-internetkabel-ethernet-verlengstuk-coupler-zwart/9200000107970662/?s2a=&bltgh=tDsYALsHNkZOnBcnqH9DoA.2_24_25.26.FeatureOption#productTitle

but is the yellow to short ?  and what is the red one ? 

I have to connect the red cable with the gray cable in the first picture, as the yellow one in the second photo is connected to the gray one. The yellow cable is from my neighbors, the red is mine.

Will this connector from the link work for this?

so far I can see the black thing you can use to make a cable longer, so normaly you do not need it. 

Hi @Milenasimao 

Up to now, I have only seen a couple of connectors. Red, yellow and white. Where do the cables come from and where do they go to?

More important: what is the KPN modem and the KPN wall socket that you have. Please show some pictures of them. What does the yellow cable from your neighbors matter? Do you share the metering cabinet with them ??