Word and Powerpoint

Hiya Vinay hope you are well

this little problem is very easy for you to fix.

When within Word or PowerPoint what you will need to do is go to the top left hand corner of your screen and click on the Office Button which will show you things like open, new and save from this menu at the bottom click the options button

You will be presented with a window that contains various options in, from the left hand side choose Proofing, after that click on the autocorrect options and then remove the tick from capitalize first letter of sentences

This should solve your trouble

Mark East