There are times when the motorway system will converge and blend/merge and separate. These are referred to as interchanges and you will be required to change lanes, perhaps more than once.
These areas can be a bit daunting, but pay attention to the signage and the overhead direction signs, and move over into the correct lane in good time. You will find that there is plenty of time and distance allowed for the traffic to make their lane and destination arrangements, but having to do this for the first time can be difficult. The best thing is to have a plan, know which motorway you will need, and if you have to change lanes/motorways, do so in good time, and double check that you have the correct lane.
If you get it wrong, never make a sudden lane change as this could result in a nasty accident. You will have to leave the motorway at the next exit and turn around, before getting back on the correct motorway.
The coming together of the numerous lanes at an interchange could mean lots of vehicles changing lanes all at the same time – clearly, this would be dangerous. To prevent this and to ease the flow of traffic, the lanes might be separated with hatch/chevron markings forming splitter islands, so stay in your lane until you have passed these.