The claims of atheists are based on their misunderstandings. If you analyse their claims carefully, you will see how their claims are false.
1. You can discuss their claims with any trusted scholar who can explain to you more facts.
2. You may read on the internet or in the library some books written to counter the misleading claims or doubts of atheists.
3. It is very useful to repeat reciting Sura al-Tawheed and LA ILAAHA ILLALLAH, and ASTAGHFIRULLAH WA ATOOBU ELAYH.