'Section 39' is 'common assault' (which can also be charged as 'battery'). While the offence theoretically carries a maximum penalty of 6 months imprisonment, the magistrates CAN'T send you to prison unless they view the matter as falling into the very highest end of 'Category 1'. A drunken brawl almost certainly WON'T fit into that category. It's far more likely to be viewed as either 'Category 2' or 'Category 3', meaning that a community order (or possibly only a fine) would be the most likely outcome. See pages 189 to 192 here:
https://www.sentencingcouncil.org.uk/wp-content/uploads/MCSG-April-2017-FINAL-2.pdf
You also CAN'T be sent to prison for criminal damage unless EITHER you went on a sustained spree of causing such damage (e.g. slashing the tyres of every car in a street) OR the value of the damage exceeded £5000. The level of damage resulting from most drunken incidents doesn't normally fall within those categories. Once again, you're facing either a fine or a community order, depending upon the cost of the damage caused. See page 43 from my link.