Isobars : meteorology

Hello Folks. I am a student of meteorology. I am struggling to understand how to draw Isobars on synoptic chart. On YouTube and other platforms the only examples i could find were using charts from United States and those charts are very simplified for learning purpose. The pressure values are shown in whole number form and as well as at intervals of 4 mb. But the chart i am given has decimal values also and is from another continent.

Is the standard isobar interval same throughout the globe? i.e 4mb

The decimal value plays a role while sketching the isobars or not. I mean, should the isobar going through 1020.7 can also be going through 1020.4?The given chart is so big how to find the right direction and a starting point?

I would be really grateful to the community for helping me to start understanding it and pointing me how proceed in understanding synoptic meteorology. The link to the map i am supposed to work is here https://ibb.co/fSHDGmR