Big data analysis - What statistical method should I use?

I am currently working on my master thesis that is investigating textual factors of "viral headlines".

My professor gave me a data set for R that contains about 4.000 packages. Each package has about 3 -5 different headlines of the same article, and their resulting click rate. Somewhat like an A/B test, where the writers tried out different versions of headlines for their articles before deciding with which headline they actually went (see a graphical representation of dataset attached). Now my question:

What statistical method should I use to analyse this data in R?

For example, I would want to investigate if a longer headline leads to more or fewer clicks? However, the packages all have a different n and as mentioned above I have about 4.000 of them.

Your help is greatly appreciated! Thanks in advance
Visualization of Dataset.jpg
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