The only options before the jury are 2nd degree murder or 3rd degree manslaughter. He couldn't be charged with 3rd degree murder because that is accidental killing whilst engaged in a felony. This is applicable in only 3 states I believe,
In any event 2nd degree murder carries a maximum sentence of 25 years, and 3rd degree manslaughter 40 years. These numbers are for minessota, other states have life imprisonment for 2nd degree murder.
We don't actually know how George Floyd died yet. The prosecution say he was asphyxiated due to chest compression, the defence say he had a heart arythmia. They are both, according to their opening statements, going to produce medical examiners to support their claim. If the defense sell the dodgy heart story Chauvin probably walks away. If the jury believe the asphyxiation Chauvin goes down for 3rd degree manslaughter.
Right now everyone is basing their judgement on social media videos, it's not really how the legal system is supposed to work.