How to increase the bottom offset??

Hello,
I am using addthis floating share button, which is showing below the screen. Therefore, it is hiding my bottom menu partly. So, I want to increase the bottom offset, so that my purpose is served. I tried some code from custom css at customization. That is not working. Here is the code-

/* footer bottom offset css */
	#bottom-footer {
	bottom: 100px
}

I also tried editing css from the child theme. Here it is-

#bottom-footer {
    background-image: none;
    background-attachment: scroll;
    background-repeat: repeat;
    background-position: 0 0;
    background-color: rgba(0, 0, 0, 0.2);
    font-size: 13px;
    padding: 8px 0;
	bottom: 100px;

Please help me to solve this. Please have a look from mobile device on the blog for better understanding my issue

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