Okay, you are right, forget about the dial. The most important is, that on the hanger you are able to switch to the biggest chain ring as well (you might not ever use it but more on this later).
What you experience is normal, shifting to the biggest changing needs way more effort than to the smaller. This is in a simplified manner is because of 2 things.
1., The front derailleur has a strong tensioned spring. Without the shifter cable, it would change to the smallest ring. To stop it, you use the screw on the lever. If the lever's screw is tightened enough to stop the derailleur to move on its own, but is loose enough that you can move it, it is the right setting. Nothing else stops the derailleur than that screw, that is why its called friction shifting, since only the friction caused by that screw (it presses the two halves of that lever together and there are washers inside as well, also bent ones acting as springs) holds back the lever - and therefore the derailleur - from moving on its own. By pulling the lever, the spring is working for you, but when you try to push forward on the lever, you are working against that spring, therefore you need bigger effort.
2., You might have noticed, that the chain is really long and its running through an also spring loaded arm in the read derailleur. That arm is responsible to keep the chain tensioned. To switch to bigger cogs (no matter if at front or at back) the arm moves forward, tensioning the spring. To change to the bigger cog you work against 2 srprings.
2+1 by the nature of shifting cables there is some unwanted/uncontrolled friction between the cable and its bousing. You might want to keep the cables oiled and/or greaseed. E.g. spray at least some wd40 into the cable housing, but make ssure to cover the wheels and the brakes with a cloth while you are doing it.
Now the fun fact. Based on this type of shifter I assume you might have an 3x6 or 3x7 setup (3 rings front, 6 or 7 at the back), Once you try shifting while pedaling, you will notice that you need a lot more force to pedal when the front is on the biggest chain ring, so at least for now, you might not want use it.
My personal tip, but others might disagree.... keep the front in the middle ring, and you can switch the back to any of the cogs (I assume, pushing forward will result in switching to bigger cog in the back). Big rear cog = easy pedaling, but slower speed, small cog, harder pedaling but the bike goes faster. Only use the smallest chain ring in the front, when the back is on any of the 2 biggest ones --> e.g. you pedal using the middle in front and smaller in back for a nice tempo when you see a hill coming up.... first switch the back to the larger/largest cogs, and if the pedaling doesn't get easy enough, then switch the front to the smallest. Vice versa... Lets say you reach the top and from there there is plains.... to go faster, switch front back to the middle gear (pedaling needs a little bit more power, but the bike goes faster) then switch the back to smaller cogs and the pedaling will become more labor intensive with every change. But also your bike will go faster. If you feel that you have to pedal too fast to make the bike even faster (what you will hardly ever feel, unless you go downhill at places where you should not try) switch the front to the biggest chain ring. The pedaling will become hard, but with every "step" you will feel that you move the bike forward.
Maybe it was a bit too long for the topic, but I hope it gets you to discover bike riding better and helps to get experience.
Lattz