Errors:  

- for

- very big effect

- very harmful for

- is not fine after the used

- their also effect

Corrected version:

There is little doubt that children fully depend on computers, and it has a significant effect on their education and life. Moreover, computers can be harmful to our health; for example, our eyes may not be fine after the use of computers, and they also affect our reading and writing skills. 

Improved version:

It is undeniable that children's reliance on computers profoundly influences their educational and personal development. Furthermore, excessive computer use can adversely affect our health, impairing our vision and diminishing our literacy skills.

Errors:  

- formost

- at all cost

- teach

Corrected version:

To begin with, the foremost reason is that teachers should avoid using computers in the classroom at all costs and return to traditional teaching methods. Moreover, the use of modern technology in the classroom nowadays has negative effects on children's health and learning skills.

Improved version:

Initially, the primary concern is that educators should minimize the use of computers in the classroom to preserve traditional teaching methodologies, which are believed to be more beneficial for children's health and cognitive development.