I'll use the term hemisphere for simplicity even though I don't believe we are on a sphere. The northern hemisphere being the part inner part of our plane surrounding the north pole, and the southern hemisphere being the outer part of our plane beyond the equator. During the northern hemisphere summer the sun is circling between the equator and the tropic of cancer. This lengthens our days in the northern hemisphere as the sun casts its light on this part of the plane for more hours of the day. As the sun moves between the equator and the tropic of Capricorn, the southern hemisphere will experience more sun/day light and the northern days will shorten.

Honestly you probably won't be able to take a look at any of this unless you first come to find that almost everything organizations like nasa tell us about space is fake. I first found out the moonlandings were complete hoaxes from a Hollywood studio. Then I found the ISS was completely fake. Then I found all satellites and images/video of space was fake including our blue spherical earth. And at that point I realized what we are told about cosmology is all lies. I would investigate these things first before flat earth if I were you, because you can't skip steps when going up the staircase of disbelief, it's just too much of a leap.