Present Tense Vs. Can

Sometimes it is okay to use present tense over 'can' in Turkish. They mean just the same.

for example;

*How can you believe this?

can be translated in more than one way.
Buna nasıl inanabilirsin? is 'one to one' translation.
You can also say Buna nasıl inanırsın?/How do you believe this? without using can/-ebilmek .
Using the continuous present is also okay - inanabiliyorsun/inanıyorsun

*When you ask for someone to do something, again it is possible to skip -ebilmek
For example;
Kapıyı açar mısın? Kapıyı açabilir misin?
The second one-with can/ebilmek sounds a little bit more polite but they mean exactly the same.

*Let's say you share your near future plans;
Bugün işe gidebilirim. Today I can go to work.
Bugün işe giderim sanırım/sanıyorum
You can add the word 'sanırım' (I guess, I assume) to your present tense sentence to make it sound less certain, or in Turkish we say 'açık bir kapı bırakmak' . You can leave an open door for uncertanity.