Hi flohof,
Thanks for coming to Apple Support Communities for help today.
This page has some suggestions that may help if your Mac is running slowly: If your Mac runs slowly.
Starting up in safe mode can clear cache and also prevent third-party programs from launching that may be interfering with performance. Here's How to use safe mode on your Mac.
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- Shut down your Mac.
- Turn on your Mac and continue to press and hold the power button until you see the startup options window.
- Select your startup disk, then press and hold the Shift key while clicking “Continue in Safe Mode.”
- Log in to your Mac. You might be asked to log in again."
You may be able to get more life out of your battery. Optimizing the settings can help as well as other tips found here: Batteries - Maximizing Performance.
"Optimize your settings.
Energy. The Energy Saver preference pane includes several settings that determine power levels for your MacBook. Your MacBook knows when it’s plugged in and runs accordingly. When using battery power, it dims the screen and uses other components sparingly. If you change this setting to maximize performance, your battery will drain more quickly.
Brightness. Dim the screen to the lowest comfortable level to achieve maximum battery life. For instance, when watching a video on an airplane, you may not need full brightness if the cabin lights are off.
Wi-Fi. Wi-Fi consumes power, even if you are not using it to connect to a network. You can turn it off in the Wi-Fi status menu in the menu bar or in Network preferences.
Applications and peripherals. Disconnect peripherals and quit applications not in use. Eject an SD card if you’re not currently accessing it."
Have a fantastic day!