كلما كانت النتيجة تعادلا، تكلم المدرب مع حارس المرمى.

كلما means whenever / every time that. It usually introduces a repeated situation, not just a single possible event.

So in this sentence:

كلما كانت النتيجة تعادلًا، تكلم المدرب مع حارس المرمى.

the idea is:

Whenever the result was a draw, the coach spoke with the goalkeeper.

By contrast, إذا often means if / when and can refer to a single event or a general condition.
So كلما is a very common way to express repeated past actions:

• كلما جاء، اتصل بي = Whenever he came, he called me
• كلما درستَ، نجحتَ أكثر = The more you study, the more you succeed (in some contexts)

Here, كلما tells you this happened repeatedly.

Because the subject is النتيجة, and النتيجة is a feminine noun in Arabic.

• النتيجة = the result
• It is grammatically feminine
• Therefore the verb must agree with it: كانت = was (feminine)

Compare:

• كان الجو جيدًا = The weather was good
  because الجو is masculine

• كانت النتيجة جيدة = The result was good
  because النتيجة is feminine

So كانت is used simply because النتيجة is feminine singular.

Because تعادلًا is the predicate of كانت, and the predicate of كان / كانت is normally in the accusative case.

In Arabic grammar:

• كان / كانت raises its subject
• and puts its predicate in the accusative

So:

• النتيجةُ = subject of كانت → nominative
• تعادلًا = predicate of كانت → accusative

That is why you see the -an ending in fully marked Arabic:

كانت النتيجةُ تعادلًا

In normal unvowelled writing, people often write simply تعادلا or تعادلًا, but grammatically the intended form is تعادلًا.

Because here it is being used as an indefinite predicate: a draw.

So the structure is:

• النتيجة = the result
• تعادلًا = a draw

This is very similar to English:

• The result was a draw
• not The result was the draw

Arabic often uses an indefinite noun after كان / كانت in this kind of sentence.

Even though تكلم is a past-tense verb, with كلما the whole sentence usually gives a repeated meaning in the past.

So:

كلما كانت النتيجة تعادلًا، تكلم المدرب مع حارس المرمى

means something like:

Whenever the result was a draw, the coach would speak with the goalkeeper.

So the past tense here does not mean just one isolated event. Because of كلما, it describes something that happened again and again.

Because تكلم مع means spoke with / talked with someone.

• تكلم by itself = spoke
• تكلم مع فلان = spoke with someone

So:

• تكلم المدرب = The coach spoke
• تكلم المدرب مع حارس المرمى = The coach spoke with the goalkeeper

This is a very common pattern in Arabic. Another common verb is تحدث مع:

• تحدث المدرب مع حارس المرمى

This would also mean The coach spoke with the goalkeeper.

حارس المرمى is an iḍāfa structure, often called a genitive/possessive construction.

Literally, it is:

• حارس = keeper / guard
• المرمى = the goal

So حارس المرمى literally means keeper of the goal, i.e. goalkeeper.

Important things to notice in an iḍāfa:

1. The first noun usually does not take الـ
2. The second noun determines definiteness

So:

• حارس مرمى = a goalkeeper
• حارس المرمى = the goalkeeper

Because المرمى is definite, the whole phrase becomes definite.

Because المدرب means the coach, not just a coach.

The الـ makes it definite:

• مدرب = a coach
• المدرب = the coach

In this sentence, the speaker is referring to a specific coach, so المدرب is definite.

Yes. In fact, that is one of the best ways to understand it.

Because of كلما, a natural English translation is often:

Whenever the result was a draw, the coach would speak with the goalkeeper.

So if an English speaker sees Arabic past tense in both clauses, that does not always mean a one-time completed event. With words like كلما, it often expresses repeated past behavior.

Yes. The clause

كانت النتيجة تعادلًا

is a normal كان sentence:

• كانت = the verb
• النتيجة = the subject of كانت
• تعادلًا = the predicate of كانت

This is a very standard pattern in Arabic. You could think of it as:

The result was a draw.

So when كلما is added, it becomes:

Whenever the result was a draw...

Yes. Arabic often allows more than one natural phrasing.

For example, a speaker might also say:

• كلما انتهت النتيجة بالتعادل، تكلم المدرب مع حارس المرمى
• كلما كانت المباراة تنتهي بالتعادل، تكلم المدرب مع حارس المرمى

These alternatives are a bit different in nuance, but the main idea is similar.

Your original sentence is grammatically clear and easy to understand. The main grammar points are the use of كلما, the feminine verb كانت with النتيجة, and the accusative predicate تعادلًا.