@siebolt is right, you can usually use "so". It can mean slightly different things depending on where it is in the sentence and what it does.
When così modifies something it usually means this, that or so:
- Le gonne non sono corte/The skirts are not short
- Le gonne non sono così corte/The skirts are not [so/this/that] short
- Noi non siamo stanchi/We are not tired
- Noi non siamo così stanchi/We are not [so/this/that] tired
And you're right, other times it translates to this way, that way, like this, like that...:
- Gli animali non mangiano così/Animals do not eat [like this/like that/this way/that way...]
- Noi non cuciniamo la verdura così/We do not cook vegetables [like this/like that/this way/that way...]
Learning adverbs, prepositions, conjunctions and the rest can be quite a challenge because it is nearly impossible to always have them translate one to one. That's the beauty of language. It also means you've just picked up a very versatile word that you will end up using every ten minutes in normal conversation ;)
Your answer has a different meaning.
"It is not (that) easy," means it is more difficult to do than it seems. Braiding hair (plating hair) looks easy but it is not that easy! "It is not that likely," actually refers to the chance of it happening. For example: It is not likely I will be hit by a lightning bolt today.
Hope this helps Robert!