Tuning your guitar, in one minute
A guitar that sounds wrong puts people off faster than any difficult chord. Start every session by tuning: one minute, and everything sounds better.
The six open strings, from the thickest to the thinnest: E, A, D, G, B, E. Play one, just one, let it ring, and see whether you are flat or sharp.
Always tune upwards. If the string is sharp, go below the note and come back up slowly: it holds better that way.
A new string keeps stretching for two or three days. Your guitar is not bad, that is normal — tune again before each session.