Downgrade to Lollipop from Marshmallow

Is there way to downgrade my system to Lollipop from Marshmallow if I installed it through OTA? I am too tired of this bugs. Even after few hard resets there are lags in any browser except Google Chrome Beta, 3D games are very laggy with a strong sound breaking up (for example Grim Fandango and Game of Thrones imposssible to play) and I have a problem with Caller ID. I can't see names of people who stored in my contacts base with international phone number. Only regional. Lollipop worked as a charm. Thanks in advance.

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