Boertjie, where abouts do you live? Maybe someone with a CTX lives close to you and can give you some pointers. This being your first detector can make understanding it's settings more difficult. You can't really set it wrong per say. You can find lots of stuff with different settings. But when you have the settings adjusted to suite your ground and hunting environment, you will have an easier and more successful time with it.
The first thing you need to know so you can optimize the setting is what kind of ground are you hunting in concerning mineralization? You can bury a clad quarter at 6" and see how good the signal is both the audible signal and the display numbers. You want good repeatable tones and the display to be repeatable with little jumping around. Then you can bury the quarter at 8" and repeat. Keep going deeper and see how deep you can go before you loose the signal. You can also dig a hole about 6" and run a strong magnet around in the loose dirt in the hole and see how much stuff sticks to the magnet. If you get a fair amount of stuff attracted to the magnet and your depth for the quarter is 8" or less, you can know the your ground is heavily mineralized. If your get 10" of depth on the quarter, you have a medium ground and if you get 12" or deeper on the buried quarter, you ground is low in mineralization. Mineralization means who much natural iron your ground has in it. The more mineralized the ground is, the harder it is for your detector to see thru it and the depth will suffer. Ground conditions can change rapidly but most of the time, it will remain reasonably consistent in a local area. How deep you are finding coins is a good way to determine the ground conditions.
Also get familiar with you sensitivity settings and know how to find it in the menu and adjust it. This will help you with determining your ground mineralization and will allows you to run the CTX as hot as possible without getting too much chatter and/or falsing. There are other things that effect the sensitivity like EMI so learning to noise cancel will help you be able to run at a higher sensitivity giving you more depth.
Ground balancing can also be a help if you have a lot of mineralization so learn to ground balance and know how to get to this on the menu incase you have to use it. It is easy to do. Ground balance allows the detector to ignore the ground signal. The detector puts out a signal into the ground and receives the signal back into the coil. All ground will have produce a signal. The more mineralized the ground is, the stronger the ground signal will be. Ground balancing will allow the detector to compensate for this by being able to separate items from the ground which in turn give more accurate and stable readings and better target separation.
Iron junk in the ground is always problematic. As Iron junk deteriorates, the rusted iron particles start leaching into the ground around the iron object. This has a tendency to "blend" the iron object into the ground. This makes it hard for a detector to separate the iron object from the ground since the iron rust fades into the ground. Since there is no sharp distinction between the object and the ground due the to the rust blending the object into the ground, it can give some false signals. Having a better idea of what kind of ground you have will help to set the CTX so that you can better deal with any iron junk in the ground.
If you hunt around old home sites that have a lot of rusty nails and other iron debris, you can save yourself some troubles by buying a magnet on wheels used to pick up nails, Roofers use these a lot to pick up fallen roofing nails. A good rake can also help to remove some of the junk. Also when detecting, when you encounter a large piece of iron junk, dig it up and get it out of the way. Sometimes you have to be pro-active and purposely dig iron junk so you can get to the good stuff. You need to determine first if the home site is worth prepping first by detecting further out from the house where the junk is less concentrated and see if you can find any coins. Some old house sites are full of junk and void of coins. People didn't have much money in those times and you can't find what isn't there.
Once you determine your ground mineralization and get familiar with your sensitivity, noise cancel and your ground balance, then we can move forward with the rest of your CTX setting and working on a discrimination pattern and tone selection for your hunting environment.