[BlindMath] Seeking solution for small problems in mathematica

[Sukriti Suri]

Greetings
This is Sukriti Suri. I am using wolfram cloud online on my macbook air 2020. The very first problem that I have encountered is the issue of not being able to evaluate a particular cell. Staying in a cell, if I press shift+enter(return),  all the cells are evaluated instead of the current one. The ideal way to do away this is to select the cell which i want to evaluate. To do so, I have tried selecting characters by holding the shift key and pressing right or left arrow. However, this selects all the cells.
Another problem being faced is the issue of not being able to edit my inputs. Howsoever hard I try, I am landed to output again despite bringing the cursor to required place.
Guidance on above matters from the users of wolfram online and mathematica is appreciated. If anyone is using mathematica software instead of wolfram online, can you please confirm if these issues are there in this software also or glitch is with online platform only.
Thanks in advance

SUKRITI SURI