Best sources(Free) to learn or start some programming languages during corona outbreak.

1. JavaScript

   Today,s web language yes you heard it right JS or javascript, no good    
   website is complete without javascript some goodresources for learning 
   javascript
     1. FreeCodeCamp by quincy larson(best)
     2. MDN Docs for javascript or javascript.info
     3. Then a good book for clearing out some topic.
    and read articles for some specific topics to make a good grasp of some 
    important topics.
   

2. Java

   I think there are plenty of good resources out there on internet for 
   learning java some of them from which i have learned are
      1. java by navin reddy* - youtube
      2. JAVA: the complete reference by herbert schildt*. 
      3. JAVATPOINT 
      4. journal dev
      5. w3resource java excercises(they are topic wise)
   

3. C#

      1. *KUDVENKAT* best to learn C# or .net framework from scratch             
      2. microsoft docs (little bit confusing)
      3. C-sharp corner
   

For improving your problem solving capabilities do more and more programing on paper first then on IDE and Find problems by dry runnning them not by compiling.