Trying to reduce the size of the adsense ads, but can’t see any place to do that on the google site. Anyone know please?
reduce it how? There are preset ad sizes in adsense. You can tweak them somewhat but I won’t recommend it.
You can use all different Ad Formats that AdSense offers: https://www.google.com/adsense/static/en_US/AdFormats.html
other then that you are not allowed to modify the size via script or with other means
For the normal users Adsense itself providing a number of Ads sizes. But I have heard that we can customize our ads, only if we receive a payment of 2235$(100000 INR) in single payment. I am not sure about it.
Only premium publishers have different rules and more variety in AdSense formats but to become a premium publisher you need several millions of page impressions per month for one webproject of yours.
The earnings you mentioned are much to low to be interesting for google 
Thank you buddy, but how to become a premium user??? Do we need to pay an extra for that or?
No. Generate 10 Million or more page impressions per month with one web project of yours that is monetized via AdSense on a consistent basis and Google will contact you.
Many thanks 