iPhone randomly loses internet connection even though still connected to the wifi network.

Connecting to Wifi is the first part and then getting connected to the Internet is the second

1. If you connect to Wifi, doesn't necessarily mean you are connected to the internet. If you are not connected to wifi could be a problem with iPhone settings or Router/Modem Settings
2. If you are not connected to the internet is the sole issue of Router / Modem Settings. Contact your ISP immediately

Check your WiFi Router / Modem for --> Recommended settings for Wi-Fi routers and access points ...

For your Internet connection.

• Over Cellular: contact your Carrier (Cellular Service Provider). The agency who issued the SIM to you
• Over WiFI: Contact your ISP (Internet Service Provider), the agency who provided the Internet Service on your Modem/Router to you

However --> Connect iPhone to the Internet - Apple Support

tomas24agustin wrote: "Let’s say it wasn’t a genuine replacement, it has something to do with my problem?"

Yes. Apple says: "Repairs performed by untrained individuals using nongenuine parts might affect the safety of the device or might cause improper function." Source:

About genuine iPhone batteries

And you "verify if it’s that the problem indeed" by replacing the fake battery (which itself is a safety risk) by a genuine iPhone battery:

iPhone Battery & Power Repair

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tomas ~ Was it changed by a qualified technician using a genuine iPhone battery?...

About genuine iPhone batteries

Repair Provider Verification - Official Apple Support

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tomas ~ Does your iPhone X still have its original battery?

And what's the Maximum Capacity % here?...

Settings > Battery > Battery Health & Charging

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