#1
Hello, does anyone know how to tune a guitar in a simple way?

Not that way you say oh Strum string A & then check string C? I am a beginner !
#2
Get a tuner.
Otherwise you can tune the strings to each other but they wont be in any specific tuning, and it can be hard without a trained ear.
#3
the most basic way to tune ur guitar to standard tuning without cheating and using an actual tuner is to find the low e on a piano or somethin and tune the open e with that, then play the 5th fret of e and tune the open a string to match the 5th fret of e, keep doing this for all the strings except the b string, where u match open b with the 4th fret of g

if u r not able to do this, use a piano and find the notes and tune them to sound the same, or just get a tuner or find an online tuner
#4
Definitely get a tuner.
If you cant get your hands on one, the most common way to tune is by intervals.
Hopefully your low E string will be fairly close, since its the thickest it usually takes the longest to go out of tune. Try to find another guitar or piano or something to get it perfect then:

Play the sixth string at the fifth fret, then tune your open fifth string until it they sound the same.
Play the fifth string at the fifth fret then tune your open fourth string until they sound the same.
Play the fourth string at the fifth fret then tune your open third string until they sound the same.
Play the third string at the fourth fret, then tune your open second string until they sound the same.
Play the second string at the fifth fret then tune your open first string until they sound the same