You need to use verbs in the present forms followed by the word つもり to describe your future intention or plan.

きょう　マクドナルド　に　いく　つもり　です。

I am planning to go to MacDonald's today.

* いく is a verb in plain forms, which means "go". つもり follows a verb in plain forms, いく.

* You cannot use polite forms with つもり. Thus, きょう　マクドナルド　に　いきます　つもり　です。is grammatically incorrect.

きょう　としょかん　で　にほんご　の　べんきょう　を　する　つもり　です。

I am planning to study Japanese at the library today.

きょう　は　おさけ　を　のまない　つもり　です。

I am not planning to drink alcohol today.

*のまない is a negative plain form of のむ, which means "drink"

References:

Introduction to Plain Forms

https://anchor.fm/yuya-sato/episodes/Introduction-to-Plain-Forms-enp0g3

Actual Conversations Using Plain Forms

https://anchor.fm/yuya-sato/episodes/Actual-Conversations-Using-Plain-Forms-enqrpc

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