Sorry to be the bearer of bad news, but have you read through this thread:
Golf 118 TSI Engine Failures and Service Campaign 24S4
Based on the symptoms you're describing, you may well have a damaged piston and loss of compression in cylinder 4. 118TSI twincharged engines (particularly those built in the early days) are extremely well known for this problem. I'd strongly suggest you get a compression test done ASAP and don't drive the car in the meantime. There's a decent chance you'll need an engine rebuild. If this is the case, a replacement coil pack will certainly not make the car drivable.
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